v5.2: stability and polish — deep-audit bug fixes + install-flow fixes

Verified findings from a multi-dimension code audit, plus the two install-flow bugs:
- Fix Opus encoder use-after-free on a codec/rate change while streaming (guard swap vs encode).
- Fix "both" single-file recording dropping audio + drifting (drain both directions in lockstep).
- Fix broken clip counter, UPnP teardown on exit, auto-update-restart foreground grant, and a
  malformed-Opus-format packet orphaning a playout session forever.
- Post-install relaunch now respects start-minimised; uninstall is path-aware so it won't clear a
  different copy's run-at-startup.
- Perf/hygiene: cache AppConfig off UI hot paths, fold per-peer EQ+gain into one pass, deterministic
  disposal (tray menu, timers, COM shortcut, Process handles, process meter), ring-buffer overflow
  guard, receiver session-lock fix, remote-control allow-list moved onto the UI thread.
- Remove dead code (two IsAsioBackend, SessionPlayout.Reset, IsSameEndpoint, RemSoundUpdater
  IDisposable); several stale-doc fixes.

Deferred (not in this release): drift-estimator tweak, peer-discovery pruning, uninstall retry-loop,
encryption nonce. Wire format unchanged (interops v3.3-v5.1). Version -> 5.2.

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

RELEASE_NOTES.md

@@ -1,38 +1,36 @@
-# RemSound v5.1
+# RemSound v5.2
 
-Install RemSound as a proper Windows app — or keep running it portable, whichever you prefer.
+A stability and polish release. No new features — this one is bug fixes and internal tidy-ups from a deep code review, so it should just feel a bit more solid.
 
-## Install RemSound on this PC
+## Fixes you might notice
 
-A new **Options → Install RemSound on this PC** turns the copy you're running into a properly installed Windows app:
+- **Changing the codec or send rate while streaming** could, in rare cases, crash RemSound with no warning. Fixed.
+- **Recording "both sent and received" into a single file** could lose small amounts of audio and drift out of sync over a long session. It now stays sample-accurate for the whole recording.
+- **After installing**, RemSound now honours your "start minimised" setting on the first relaunch (and still comes to the front when you're not starting minimised).
+- **Uninstalling** one copy no longer switches off a different copy's "run at startup".
+- Starting a split "received only" recording with **no peers connected** now tells you clearly, instead of quietly making an empty folder.
+- The **clipping indicator** in the diagnostics works again.
 
-- It sets RemSound up on the **Start menu** (with the program, the manual and an uninstall shortcut), adds a **desktop shortcut**, and lists it in Windows' **Installed apps**.
-- It installs into your own user area, so it **never asks for administrator rights** and only affects your account.
-- A tick-box dialog lets you choose what to set up — desktop and Start-menu shortcuts, run at startup — and bring your **profiles and settings, recordings and logs** across from the copy you're running.
-- When it's done it reopens from the installed location; everything carries on exactly as before, and RemSound still updates itself in place as usual.
+## Under the hood
 
-Once it's installed, that same menu item becomes **Uninstall RemSound from this PC** (with matching entries in the Start menu and Windows' Installed apps). Uninstalling asks first, with two tick-boxes — **remove profiles, config and logs**, and **remove recordings** — both off by default, so your own files are kept unless you say otherwise.
-
-You never *have* to install: running RemSound straight from the unzipped folder works exactly as it always has.
-
-## Smaller download
-
-The built-in cue sounds have been slimmed down, so RemSound is a smaller download and takes up less space.
+- The automatic-update restart now brings the window to the front, the same way the installer does.
+- The router port opened by UPnP is properly removed when you close RemSound.
+- Lighter on memory and disk — fewer background file reads while you work, and tidier release of resources when the window closes or switches profiles.
 
 ## Compatibility
 
-The over-the-network format is unchanged, so **v5.1 talks to v3.3 through v5.0** with no trouble — you don't have to update both ends at once. (Everyone still needs **v3.3 or newer**, where end-to-end encryption came in.)
+Nothing about the over-the-network format changed, so **v5.2 talks to v3.3 through v5.1** with no trouble — you don't have to update both ends at once. (Everyone still needs **v3.3 or newer**, where end-to-end encryption came in.)
 
 ## Install
 
-1. Download `RemSound-v5.1.zip` from this release.
+1. Download `RemSound-v5.2.zip` from this release.
 2. Close RemSound.
 3. Extract the zip **over your existing RemSound folder**, overwriting program files when prompted. The zip is program files only — it won't touch your settings, profiles, logs or recordings.
-4. Run `RemSound.exe`. (If you'd like it set up as a proper Windows app, use **Options → Install RemSound on this PC**.)
+4. Run `RemSound.exe`.
 
 ## Upgrading
 
-**From v3.6 or newer:** Help → Check for updates installs v5.1 with the in-app updater — and if it can't finish, it puts your old version back exactly as it was.
+**From v3.6 or newer:** Help → Check for updates installs v5.2 with the in-app updater — and if it can't finish, it puts your old version back exactly as it was.
 
 **From v1.9–v3.5:** Check for updates works, but uses your current version's older updater for this one hop. If auto-update has been failing on your machine, install by hand using the steps above.