Add procedural crowd ambience and radio crackle

- AudioFeedback.start_crowd_bed() builds a 4 s looping AudioStreamWAV at runtime
  (one-pole filtered noise plus a 68/103 Hz drone, seeded) and set_crowd_level()
  maps crowd mood 0..1 to -34..-12 dB, so the street gets louder as it gets
  agitated or panics. The bed starts with the shift and stops at shift end.
- play_radio_open()/play_radio_close() push short filtered-noise bursts; wired to
  opening the radio panel, submitting a report, cancelling, and closing the panel.
- Still asset-free and headless-safe: with a dummy audio server the calls no-op.
  _free_player() returns null before _ready and callers handle it.

Tests/docs
- Headless suite 127 -> 134 (test_audio_feedback.gd).
- New smoke_audio.gd: bed playing, level follows mood events, radio crackles once
  per open/close, bed stops at shift end. Verified windowed (real audio server).
- README, TODO section moved to DONE, MEMORY. Version 0.2.8.

MEMORY.md

@@ -21,8 +21,8 @@ Session memory for durable decisions, state, and gotchas. Keep concise, remove o
   Windowed control smoke: `godot --path . --script res://src/test/smoke_focus_radial.gd` → exit 0.
 - `main` is in sync with origin. **v0.2.2** tags the session-shell + world-follow-up commit;
   CI builds the portable binaries, NSIS installer, and AppImage on the tag push.
-- Next work: `TODO.md` audio (crowd bed rising with mood, radio crackle), then accessibility and
-  scenario content.
+- Next work: `TODO.md` accessibility (grayscale-safe escalation cues, HUD font scale in settings),
+  then scenario content gaps.
 - Do not re-open `override_access`. Do not bind wand to `W`. Do not remove the radio easter egg.
 
 ## Current State
@@ -95,6 +95,11 @@ Session memory for durable decisions, state, and gotchas. Keep concise, remove o
   `_begin_incident()` now starts one per focused NPC (`has_open_incident()` guard), verbs call
   `_ensure_incident()`, and `ShiftCoordinator._finish_shift()` closes leftovers as `unresolved`
   before building the review.
+- **Audio (2026-10-31):** `AudioFeedback.start_crowd_bed()` builds a 4 s looping `AudioStreamWAV`
+  (one-pole-filtered noise + 68/103 Hz drone, seeded) and `set_crowd_level(mood)` maps 0..1 to
+  -34..-12 dB. `play_radio_open/close` push short filtered-noise bursts. All procedural; with a
+  dummy (headless) audio server the calls are no-ops. `_free_player()` returns null when `_ready`
+  has not run (tests), and callers handle null.
 - **NPC theater (2026-10-31):** `NpcAvatar.theater_pose()` maps `intent` + `arrived` to
   idle/sit/photo/film/perform. Pure helpers `crouch_for_pose`, `prop_lift_for_pose`,
   `sway_for_pose` keep the math testable. Sit lowers the rig by 0.34 and swings the legs forward