v3.4 refinements: WASAPI drift correction, startup-dialog sequencing, quick-switch polish, docs

Builds on the v3.4 freeze (dd70613) with the fixes and tuning from live testing,
plus the v3.4 documentation pass.

Audio (receiver):
- Per-device WASAPI drift correction in MultiOutputPlayout. A pull-side resampler
  (mirroring SessionPlayout's proven corrector) holds each output device's buffer at
  a fixed low depth, cancelling the slow clock drift that made WASAPI peers "lag
  apart" over long sessions. Feed-forward clock-ratio measurement plus a gentle
  depth-restoring term; the first measurement window is discarded because WASAPI
  start-up priming poisons it. ASIO already self-corrected; this brings WASAPI level.
- Output device buffer requested at 5 ms (WASAPI clamps it up to the device's minimum
  period, ~10 ms) instead of 15 ms, since the corrector keeps it fed — a free saving.

UI / accessibility (MainForm, Program):
- Startup notices (what's-new About box, Realtek warning) now run one at a time via a
  single sequence instead of separate BeginInvokes, so they no longer stack into
  nested modals that couldn't be closed. The loading splash is skipped for a
  tray-bound quick switch.
- Quick profile switch keeps RemSound in the tray if it was there, and plays the
  switch cue immediately on click.
- Profile-switch cue now plays on click for every switch path (recent menu, quick
  switch, File > Open) and no longer on a fresh start into the first profile. It was
  also previously dead on the rebuilt form (pendingProfile was nulled first).
- Realtek ASIO toggle's accessible name now reads "Enable"/"Disable" to match the
  visible text, instead of "Toggle" (screen reader read the wrong word).

Docs (plain English):
- RELEASE_NOTES.md: v3.4 entry.
- About dialog: v3.4 "what's new".
- readme.html (the canonical bundled manual): quick switch, the hotkey read-outs, the
  new profile-menu-open cue, Realtek auto-detect/disable, and the config-folder path.
- MANUAL.md regenerated from readme.html via sync-manual.py so the two stay in sync.

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

src/RemSound.App/AboutDialog.cs

@@ -20,6 +20,41 @@ internal sealed class AboutDialog : Form
     /// updates" path.</summary>
     private const string ReleaseNotes =
         """
+        RemSound v3.4
+
+        Quick profile switch: a new global hotkey pops up a
+        list of all your profiles from anywhere — even when
+        RemSound is in the system tray. Arrow to one, press
+        Enter, and it switches straight away. It marks the
+        profile you're on, plays a sound as the list opens
+        and again when you switch, and stays in the tray if
+        that's where it was. Unset by default; give it a key
+        under Options → Keyboard shortcuts.
+
+        A safety net for the Realtek ASIO driver, which leaks
+        Windows resources and can make audio unstable: RemSound
+        now spots it on startup and offers, just once, to
+        disable it. Re-enable or disable it any time from the
+        Options menu.
+
+        Your screen reader now reads out global hotkeys when
+        you move over the menu item or control they're tied to,
+        so you can learn your shortcuts just by arrowing around
+        — no need to open the shortcuts dialog.
+
+        Smoother long sessions on WASAPI: two machines' sound
+        clocks drift apart by a hair over time, which slowly
+        added delay. RemSound now corrects that continuously,
+        so a WASAPI link stays as tight after three hours as it
+        was at the start. (ASIO already kept itself in step.)
+
+        Also: a new "profile menu open" cue; the profile-switch
+        cue now plays the instant you switch, and no longer on
+        a fresh start; faster reaction when you plug or unplug a
+        device; and your settings now tuck into a "config"
+        folder, moved there automatically the first time you
+        run this version.
+
         RemSound v3.3
 
         Your audio is now encrypted, end to end, so you no