Release v3.6: rebuild the self-updater (in-app, rollback-safe); warnings to front

Replace the generated cmd.exe + robocopy update helper — which silently
failed on some machines — with an in-app C# installer:
  * Stage the new version to a per-user temp folder off the install and run
    the new RemSound.exe from there, so nothing in the install is locked by
    the updater itself.
  * Wait for the old process to fully exit (real WaitForExit), then
    back-up-and-swap files in C# with retry + rename-aside; roll the install
    back to the previous version on any failure, so a failed update can never
    leave a half-installed RemSound.
  * Log every step to updater.log; clean up old stages and legacy batch
    artefacts on launch. Removed the old BuildInstallScript batch generator.

Route the "RemSound is already running" dialog and its follow-up message
through ForegroundDialog so they surface in front from a background-relaunched
copy, matching the earlier post-update fix.

Docs: rewrite the readme update sections for the new mechanism, regenerate
MANUAL.md, refresh the About-box changelog and RELEASE_NOTES.

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

RELEASE_NOTES.md

@@ -1,45 +1,39 @@
-# RemSound v3.5
+# RemSound v3.6
 
-A reliability-and-tidiness release: sound cards recover on their own if you unplug them, the audio cushion now sizes itself to each card, everything you own lives in one neat folder that updates can't touch, and a stack of under-the-hood fixes from a top-to-bottom code review.
+A reliability release centred on updating. RemSound now installs its own updates instead of handing the job to a Windows script — so updates that used to quietly fail on some machines go through, and a failed update can never leave you half-installed.
 
-## Recover a sound card you unplug
+## Updating is far more reliable
 
-If a USB sound card you're listening through is unplugged and plugged back in, **RemSound now re-opens it automatically and the sound resumes** — you don't have to re-tick it. (This works when the card comes back as the same Windows device, which is the usual case when you plug it into the same socket.)
+RemSound used to finish an update by handing the file-swap to a small Windows batch script. On some machines that step would silently fail — you'd "update" and still be on the old version, sometimes with nothing on screen to say why.
 
-## The audio cushion sizes itself to each card
+**RemSound now installs updates itself, in its own code:**
 
-RemSound keeps a small cushion at the sound card to smooth over the tiny timing difference between two machines' sound clocks. It now **sizes that cushion to each card automatically** — a card that moves sound in bigger chunks gets a little more room, a fast interface stays tight — so there's nothing to fiddle with. It just settles on the right amount.
+- It runs the install from a fresh copy of the new version in a temporary folder, so nothing in the program folder is locked while the swap happens.
+- It waits for the old copy to fully close, then moves the old files aside and copies the new ones in — **retrying** if a file is briefly held open (by a sync app, say) rather than giving up.
+- **If anything goes wrong, it puts your previous version back exactly as it was** and reopens it. A failed update can never leave a broken, half-installed RemSound.
+- Every step is written to a plain `updater.log` next to the program, so if a problem ever does recur there's a real reason to read, not a blank.
 
-## A microphone-privacy heads-up
+Your settings, profiles, logs and cue sounds are never touched by any of this.
 
-Windows can silently block apps from using your microphone, and when it does, a mic sends silence rather than failing — easy to miss. RemSound now **warns you** when you switch on a mic Windows is blocking (including when a profile loads with one already on), and points you at the exact two Windows settings to turn on.
+## More warnings come to the front
 
-## Warnings always come to the front
-
-Even when RemSound is minimised to the system tray, an important warning — the "your files have moved" notice, a microphone warning, an update prompt — now **pops up in front with focus**, so your screen reader reads it straight away. RemSound stays in the tray; only the warning comes forward.
-
-## One tidy folder for everything
-
-Everything this machine keeps for you — your settings, profiles, logs, and cue sounds — now lives together in one folder inside RemSound called **user settings and logs**. It moves there automatically the first time you run v3.5, and RemSound tells you once. Nothing is lost. **From now on, updates never touch that folder** — so any custom cue sounds you put there survive updates.
-
-## Smaller things
-
-- **Volume and mute** now come back correctly when you load a profile.
-- A round of reliability fixes from a full code review: two resource leaks closed, profile and settings saves are now crash-safe, and a good clear-out of dead code.
+Every important notice now surfaces in front with focus, even when RemSound is minimised to the tray. v3.6 adds the last two that didn't: the **"RemSound is already running"** dialog (and its follow-up message), and the **what's-new note shown after an update** that installed while RemSound was tucked away.
 
 ## Compatibility
 
-**v3.5 talks to v3.3 and v3.4 with no trouble** — the over-the-network format hasn't changed, so you don't have to update both ends at once. (You still need everyone on **v3.3 or newer**, because that's where end-to-end encryption came in.)
+**v3.6 talks to v3.3, v3.4 and v3.5 with no trouble** — the over-the-network format hasn't changed, so you don't have to update both ends at once. (Everyone still needs to be on **v3.3 or newer**, because that's where end-to-end encryption came in.)
 
 ## Install
 
-1. Download `RemSound-v3.5.zip` from this release.
+1. Download `RemSound-v3.6.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 profiles, settings, recordings, or sounds.
-4. Run `RemSound.exe`. The first launch tidies your files into the new folder and tells you once.
+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, recordings, or sounds.
+4. Run `RemSound.exe`.
 
 ## Upgrading
 
-**From v1.9 onward:** Help → Check for updates works — it will fetch and install v3.5 automatically. If you've ticked "Check for updates on startup" and "Silently install updates", v3.5 installs itself shortly after launch.
+**From v1.9 onward:** Help → Check for updates works — it will fetch and install v3.6 automatically, and if you've ticked "Check for updates on startup" and "Silently install updates" it installs itself shortly after launch.
 
-**v1.8 and earlier:** the auto-updater in those versions has a fault that prevents it installing updates, so Check for updates will download v3.5 but not apply it. Install v3.5 by hand using the steps above — just this once. From the build you install onward, updates are automatic.
+Note that the hop *to* v3.6 still uses your current version's updater. The new, more reliable in-app installer only takes over **once you're on v3.6**. So on the rare machine where auto-update has been failing — exactly the problem this release fixes — download `RemSound-v3.6.zip` and extract it over your folder by hand, just this once. Every update after that uses the new installer.
+
+**v1.8 and earlier:** the auto-updater in those versions has a fault that prevents it installing updates at all — install v3.6 by hand using the steps above.