chat: honest local send status + sender-side pacing (Phase 5)

Closes the final phase of docs/chat-hardening-plan.md. Two problems: a
locally echoed message always looked sent even when the core had no active
session or the gossip broadcast failed; and a fast burst could broadcast
'successfully' yet be silently dropped by every receiver's per-author rate
bucket (8 burst, then 1/s) with no sender feedback.

Send status: CoreCommand::SendChat/SendChatFile carry a local-only id (never
on the wire); the core replies with UiEvent::ChatSendResult after the gossip
broadcast succeeds or fails, and a no-active-session is now an explicit
failure rather than a silent no-op. gossip send_chat, which previously
returned Ok on a missing sender/topic or an encode failure, now returns Err.
ChatEntry gains local_send: Option<LocalSend>; failed sends render a red
'Not sent — {reason}  [Retry]' line, Broadcast/Pending render nothing
(there are no delivery receipts, so silence is the honest success state).

Sender-side pacing (new src/app/sendqueue.rs): sends past the burst queue
locally as 'queued…' and trickle out at the receivers' sustained rate, so
nothing is lost and typing is never blocked (user chose queue-and-trickle
over input throttling). The pacer reuses the gossip gate's own TokenBucket +
per-author constants (now pub(crate)) so the two sides of the policy can't
drift. A 250ms drain subscription runs only while the queue is non-empty.
Retry re-dispatches the retained payload; re-serving the same attachment id
replaces the ServeStore entry rather than double-counting bytes. The pacer
and monotonic send-id counter survive a room reset (receivers' buckets
persist; ids never alias a late result); queue and retry payloads are cleared.

582 lib tests (+11: 4 pacer/queue seam, 7 app-level transition/retry/reset);
all-targets green, clippy -D warnings clean, fmt clean, smoke launch OK. No
wire change (GOSSIP_PROTO stays 5). Tests-green-only — the two owed
two-machine field-test items are logged in the plan.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

docs/chat-hardening-plan.md

@@ -1,18 +1,23 @@
 # Chat hardening — ephemeral implementation plan
 
-**Status (2026-07-18):** Phases 1–4 COMPLETE. Phase 1 = shared text policy in
-`src/sanitize.rs`, ceilings enforced at UI input, sign point, and gossip ingress.
-Phase 2 = roster-bound authorship (`src/core/chatroster.rs`), replay dedup + rate
-limits (`ChatIngressGate` in `src/network/gossip.rs`). Phase 3 = attachment
-cache/serve-store budgets, downscaled previews, auto-fetch byte/request budgets
-(`src/core/fetchbudget.rs`), exact transfers, bounded local reads. Phase 4 =
-parsed-URL link policy (`is_safe_web_url`/`link_ranges` in `src/sanitize.rs`,
-`url` crate), 8-link cap, cached link ranges in `ChatEntry`, 512 KiB history
-text budget, chat-body bidi-override strip (closes S14). All gates green each
-phase. Phase 5 not started. This is a temporary scope contract for hardening
-the existing room chat. Update the checkboxes and decision log as work lands,
-then delete this file when the work is complete. Do not add link previews as
-part of this effort.
+**Status (2026-07-18):** Phases 1–5 COMPLETE (all plan phases done). Phase 1 =
+shared text policy in `src/sanitize.rs`, ceilings enforced at UI input, sign
+point, and gossip ingress. Phase 2 = roster-bound authorship
+(`src/core/chatroster.rs`), replay dedup + rate limits (`ChatIngressGate` in
+`src/network/gossip.rs`). Phase 3 = attachment cache/serve-store budgets,
+downscaled previews, auto-fetch byte/request budgets (`src/core/fetchbudget.rs`),
+exact transfers, bounded local reads. Phase 4 = parsed-URL link policy
+(`is_safe_web_url`/`link_ranges` in `src/sanitize.rs`, `url` crate), 8-link cap,
+cached link ranges in `ChatEntry`, 512 KiB history text budget, chat-body
+bidi-override strip (closes S14). Phase 5 = honest local send status
+(`CoreCommand::SendChat`/`SendChatFile` carry a local id, `UiEvent::ChatSendResult`,
+`SendStatus` on own echoes) PLUS sender-side pacing (`src/app/sendqueue.rs`
+mirrors the receivers' per-author budget so fast bursts trickle instead of being
+silently dropped downstream). All gates green each phase. This is a temporary
+scope contract for hardening the existing room chat; with every phase complete
+and the two-machine field test done, delete this file (see the completion note
+at the end). The two-machine field-test section below is still owed before that
+deletion. Do not add link previews as part of this effort.
 
 ## Goal
 
@@ -294,24 +299,37 @@ small spans an unnecessary UI/launcher surface.
 **Target:** never present a locally echoed message as successfully broadcast when
 the core rejected it or gossip broadcast failed.
 
-- [ ] Add a local-only message id and `Pending`/`Broadcast`/`Failed` state to local
-  chat entries. Do not put this id or state on the wire.
-- [ ] Carry the local id through `CoreCommand::SendChat`/`SendChatFile` and return a
+- [x] Add a local-only message id and `Pending`/`Broadcast`/`Failed` state to local
+  chat entries. Do not put this id or state on the wire. (`ChatEntry.local_send:
+  Option<LocalSend>`; `SendStatus` also has `Queued` for the paced-but-not-yet-sent
+  state — see the pacing decision-log entry.)
+- [x] Carry the local id through `CoreCommand::SendChat`/`SendChatFile` and return a
   `UiEvent` result after the local gossip broadcast call succeeds or fails.
-- [ ] If the core is not in an active session, return failure instead of silently
-  doing nothing.
-- [ ] Show failure compactly with a retry action. A successful local broadcast must
+  (`SendChat`/`SendChatFile` gained `local_id`; new `UiEvent::ChatSendResult { local_id,
+  error }`.)
+- [x] If the core is not in an active session, return failure instead of silently
+  doing nothing. (`send_chat` now `Err`s on missing sender/topic and on encode
+  failure; the core arm maps no-session to a `ChatSendResult` error.)
+- [x] Show failure compactly with a retry action. A successful local broadcast must
   not be labeled “delivered” or “read”; PeerSpeak has no peer acknowledgements.
-- [ ] Retry creates one new signed broadcast while retaining replay correctness and
-  attachment serving state.
+  (Failed → red "⚠ Not sent — {reason}  [Retry]" line; Broadcast/Pending render
+  nothing — silence is the honest success state.)
+- [x] Retry creates one new signed broadcast while retaining replay correctness and
+  attachment serving state. (`RetryChatSend(id)` re-dispatches the retained
+  `PendingSend`; re-serving the same attachment id REPLACES the `ServeStore`
+  entry, never double-counts — see `serve_store_replacement_accounting_and_remove_clear`.)
 
 ### Phase 5 tests
 
-- [ ] Local echo starts pending, becomes broadcast on success, and becomes failed
-  on no-session/channel/gossip error.
-- [ ] Results update only the matching local entry, including after history
-  eviction or room reset.
-- [ ] Retry does not duplicate served bytes or mutate an unrelated entry.
+- [x] Local echo starts pending, becomes broadcast on success, and becomes failed
+  on no-session/channel/gossip error. (`send_status_pending_then_broadcast_on_success`,
+  `send_status_failed_keeps_payload_for_retry`.)
+- [x] Results update only the matching local entry, including after history
+  eviction or room reset. (`send_result_updates_only_the_matching_entry`,
+  `send_result_after_eviction_drops_orphan_payload`, `send_result_after_room_reset_is_a_noop`.)
+- [x] Retry does not duplicate served bytes or mutate an unrelated entry.
+  (`retry_redispatches_only_the_targeted_send`; served-byte dedup =
+  `serve_store_replacement_accounting_and_remove_clear` in `files.rs`.)
 
 ## Compatibility and versioning
 
@@ -359,6 +377,11 @@ it; do not make ordinary unit tests depend on external network access.
   rest as selectable plain text, with nothing dropped.
 - [ ] A message attempting bidi-override display spoofing renders in send order
   (the override characters are stripped, emoji/joining-script text intact).
+- [ ] Send a fast burst (>8 messages in a second): all arrive at the peer in
+  order, none silently lost; the sender sees "queued…" on the overflow that
+  then clears as each goes out.
+- [ ] Send with no active session (or a failing broadcast): the message shows
+  "⚠ Not sent" with a Retry, and Retry resends it once when connectivity is back.
 
 ## Completion criteria
 
@@ -522,3 +545,40 @@ The plan is complete when:
   an open Save/Play on an evicted line keeps its bytes-in-hand (the save
   dialog falls back to the generic "download" name). The just-pushed entry is
   never evicted; a single message's 8 KiB ceiling cannot exceed the budget.
+- **2026-07-18 (Phase 5):** Sender-side PACING was added to Phase 5's scope
+  (originally receiver-status only). The Phase 2 decision log deferred the
+  "apply the same local submit policy to accidental rapid Enter" item to pair
+  with Phase 5, and honest status alone would still let a fast burst broadcast
+  successfully yet be silently dropped by every receiver's per-author bucket
+  (8 burst, then 1/s) with no sender feedback. The user chose "queue and
+  trickle" over "throttle input": sends past the burst queue locally as
+  `SendStatus::Queued` ("queued…") and release at the receivers' sustained
+  rate, so nothing is lost and typing is never blocked.
+- **2026-07-18 (Phase 5):** The pacer (`src/app/sendqueue.rs`) reuses the
+  gossip gate's OWN `TokenBucket` + `CHAT_AUTHOR_BURST`/`CHAT_AUTHOR_REFILL_PER_MS`
+  (made `pub(crate)`), so the two sides of the rate policy are one definition
+  and cannot drift. It mirrors only the PER-AUTHOR budget, not the room-wide
+  one — we cannot know other members' send rates, and the per-author bucket is
+  the one guaranteed to apply to us at every receiver.
+- **2026-07-18 (Phase 5):** Send status renders as a line UNDER the message
+  (user pick over an inline suffix glyph); `Broadcast` and the transient
+  `Pending` show nothing because PeerSpeak has no delivery/read receipts, so an
+  unadorned message IS the honest "handed to the swarm" state. Only `Queued`
+  and `Failed` (with Retry) are surfaced.
+- **2026-07-18 (Phase 5):** The pacer and the monotonic send-id counter
+  deliberately SURVIVE a room reset while the queue and retry payloads are
+  cleared: receivers' per-author buckets persist across our rejoin (so the
+  pacer should not refill to full), and never-reused ids keep a late
+  `ChatSendResult` from a pre-reset send from aliasing a new entry — verified by
+  `send_result_after_room_reset_is_a_noop`.
+- **2026-07-18 (Phase 5):** The pacer clock is `Instant`-based
+  (`AppState.send_clock`), not wall-clock, so a system time jump can neither
+  rewind nor fast-forward the send budget.
+
+## Completion
+
+All five phases are implemented and every gate is green. Per the scope-contract
+note at the top, this file should be DELETED once the owed two-machine field
+test (the checklist below) has been run — that deletion is a separate,
+user-gated step, not part of the Phase 5 commit. Until then the plan stays as
+the record of what shipped and what remains to verify on real hardware.