host/taint: match peerspeak's second ownership carrier

The consumer half of phase 1 (plan §5.1, impl plan §3). The engine's
tag root becomes a union: `peerspeak.owned` truthy OR `node.name`
starting with `peerspeak_owned_`. Round 8 added the second carrier
because a node property is invisible to the registry `global` event
and recoverable only by binding the node — which is exactly how the
phase-5 gate failed — while `node.name` is announced directly.

The union lives in `local_root_reason`, not in the adapter. Folding
both into the one `peerspeak_owned` bool at the observation boundary
would make each carrier untestable alone, which is the phase-3r
lesson: a gate asserting a value two sources can satisfy gates
neither. The existing `peerspeak_tagged_nodes_…` fixture now carries
both carriers, so it would keep passing if either were deleted; two
new tests pin them individually, and a third pins that the prefix
matches only at the start of a name.

Both literals are now named constants — they are a cross-repo wire
contract with peerspeak, not local naming — and asserted against
tests/fixtures/ownership-tag-contract.txt, committed byte-identical
in both repos. That test also runs the fixture's own worked example
name through the engine, so the shared file cannot document a value
this side does not actually exclude.

Five mutations verified: drop either carrier, loosen `starts_with` to
`contains`, or rename either constant, and exactly the intended test
fails.

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

src/host/audit/tests.rs

@@ -22,9 +22,17 @@ use super::metrics::{BUCKET_LABELS, Metrics, QUEUE_THRESHOLD_US, Sample};
 use super::*;
 use crate::host::aec::AecConfig;
 use crate::host::observer::{EventKind, Readiness};
+use crate::host::taint::PEERSPEAK_OWNED_NODE_PREFIX;
 use crate::host::taint::fixture::{self, Graph, NodeRef};
 use crate::host::taint::snapshot::{GraphSnapshot, MediaRole};
 
+/// The `node.name` a [`Graph::peerspeak_node`] fixture produces. Built from
+/// the same constant the engine matches on, so these audit rows report the
+/// name shape a live peerspeak node actually has (v3.5 §5.1, carrier 2).
+fn owned_name(role: &str, pid: u32) -> String {
+    format!("{PEERSPEAK_OWNED_NODE_PREFIX}{role}_{pid}")
+}
+
 const AEC_MODULE: u64 = 7;
 const TIMEOUT: Millis = 5_000;
 
@@ -284,13 +292,14 @@ fn a_shut_gate_preserves_the_engines_own_reasons() {
         .body;
     let (_, excluded) = partition(&body);
 
+    let playback = owned_name("peerspeak-playback", 200);
     assert!(!body.fan_out_permitted);
     assert_eq!(
         excluded,
         vec![
             ("music", "aec-validating"),
             // Tagged, so it keeps the reason that actually applies to it.
-            ("peerspeak-playback", "peerspeak-owned"),
+            (playback.as_str(), "peerspeak-owned"),
         ]
     );
 }
@@ -457,11 +466,12 @@ fn row_1_owner_bridge_forwarder_with_an_untainted_control() {
         .body;
     let (eligible, excluded) = partition(&body);
 
+    let call_name = owned_name("peerspeak-call", 200);
     assert_eq!(eligible, vec!["clean-loopback-playback"]);
     assert_eq!(
         excluded,
         vec![
-            ("peerspeak-call", "peerspeak-owned"),
+            (call_name.as_str(), "peerspeak-owned"),
             ("tainted-loopback-playback", "tainted-owner-bridge"),
         ]
     );
@@ -494,11 +504,12 @@ fn row_3_one_tainted_module_does_not_taint_the_other() {
         .body;
     let (eligible, excluded) = partition(&body);
 
+    let call_name = owned_name("peerspeak-call", 200);
     assert_eq!(eligible, vec!["module-b-playback"]);
     assert_eq!(
         excluded,
         vec![
-            ("peerspeak-call", "peerspeak-owned"),
+            (call_name.as_str(), "peerspeak-owned"),
             ("module-a-playback", "tainted-owner-bridge"),
         ]
     );
@@ -701,7 +712,8 @@ fn the_taint_view_covers_non_candidate_roles() {
         tainted.contains(&("null-sink", "tainted-upstream")),
         "the sink is not a candidate but its taint is what explains the row: {tainted:?}"
     );
-    assert!(tainted.contains(&("peerspeak-call", "peerspeak-owned")));
+    let call_name = owned_name("peerspeak-call", 200);
+    assert!(tainted.contains(&(call_name.as_str(), "peerspeak-owned")));
 }
 
 /// A record must serialise to a single line. Newlines inside a JSON Lines