packaging(win): update INSTALL.md + README.md for 0.3.0

- INSTALL.md: bump the setup filename to 0.3.0; add an end-user section
  on text chat + sending photos/files (inline images, file chips,
  Save/Download, 25 MB cap, session-only); note that both ends must run
  the same version under "won't connect".
- README.md: add a Version compatibility section (installer version
  tracks Cargo; a 0.x MINOR bump is a breaking wire change so everyone
  must reinstall; 0.3.0 can't talk to 0.2.x).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

packaging/windows/INSTALL.md

@@ -8,7 +8,7 @@ it once, then you and I connect directly to each other.
 
 ## 1. Install it
 
-1. Double-click **`peerspeak-0.2.0-setup.exe`** (the file I sent you).
+1. Double-click **`peerspeak-0.3.0-setup.exe`** (the file I sent you).
 
 2. **Windows will probably show a blue "Windows protected your PC" warning.**
    This is normal — it shows up for any app that isn't from a big company with a
@@ -69,13 +69,39 @@ Either way works the same; it just depends on who makes the room.
 
 ---
 
+## 4. Chatting and sharing photos/files
+
+There's a **text chat** box at the bottom of the call window — type a message
+and press **Enter** to send it to everyone in the room.
+
+You can also **send a photo or a file**:
+
+1. Click the **attach button** (the small paperclip-style button) next to the
+   message box.
+2. Pick a photo or file from your computer.
+3. It sends to everyone in the room. **Photos show up right in the chat**;
+   other files appear as a small download chip with the file's name.
+
+To **save** a file someone sent you, click the **Save** (or **Download**)
+button next to it in the chat and choose where to put it.
+
+A couple of notes:
+- There's a size limit of about **25 MB** per file — bigger files are turned
+  away with a message.
+- Shared files only last for the **current call**. They aren't saved anywhere
+  automatically, so save anything you want to keep before you leave the room.
+
+---
+
 ## Troubleshooting
 
 - **"I don't hear anything."** Open Settings and pick the correct microphone and
   output device. Headphones are best — they prevent echo.
 - **"It won't connect."** Make sure you pasted the *entire* ticket (they're
   long and easy to cut off). If it still won't connect, we may just need a fresh
-  ticket — they're meant to be used right away.
+  ticket — they're meant to be used right away. Also make sure we're both on the
+  **same version** — if I've sent you an updated installer, install it (an old
+  version and a new one can't connect to each other).
 - **The blue warning again.** Same as install: **More info → Run anyway**. It's
   the unsigned-app warning, not malware.
 

packaging/windows/README.md

@@ -9,6 +9,18 @@ notification chimes, and avatar presets are all embedded in the binary
 runtime, so there are no extra DLLs to bundle. The installer payload is just the
 `.exe` plus an `.ico` for the Start-menu / desktop shortcuts.
 
+## Version compatibility
+
+The installer version tracks the crate version in `Cargo.toml` (currently
+**0.3.0**) — keep `MyAppVersion` in `peerspeak.iss` in sync when it changes.
+
+Per `VERSIONING.md`, a **MINOR** bump in `0.x` is a **breaking wire change**:
+peers on different MINOR versions can't connect (they fail fast at the
+handshake rather than misbehaving). So when you ship a new Windows build after
+a MINOR bump, **everyone on the call must reinstall** — an old Windows build
+and a newer Linux/Windows peer won't talk. (0.3.0 was the chat file-sharing +
+per-peer noise-gate release; it cannot connect to a 0.2.x peer.)
+
 ## Files
 
 | File | Tracked | Purpose |