Add session shell and close world presentation follow-ups

Session shell
- Startup venue menu (src/game/ui/start_menu.gd): keyboard + mouse, replaces
  the live-shift boot and V as the player-facing venue path (V stays a debug bind).
- Pause overlay on Esc (src/game/ui/pause_overlay.gd): resume, restart shift,
  settings, quit to menu.
- Settings panel (src/game/ui/settings_panel.gd): mouse look sensitivity and
  HUD font scale, persisted via Save into user://settings.json and loaded on boot.
- Shift review "Run another shift" now returns to the venue menu.
- New smoke: src/test/smoke_session_shell.gd (menu -> shift -> pause -> settings
  -> menu), passes headless and windowed.

World and presentation
- Skyline backdrop restored with a transparent asset and an alpha-scissor
  unshaded material; fixes the opaque black slab from the earlier attempt and
  the unimported texture path.
- Steps and landing are a StaticBody3D with per-tread colliders, so the guard
  and NPCs walk up instead of clipping through.
- Marquee Label3D scaled up (72 -> 160) so STEP LINE reads from the sidewalk.
- Focus torus and name tag enlarged for 2-3 m readability.
- Routine traffic despawns after an idle lifetime (NpcAvatar.ephemeral), so the
  16-NPC cap no longer fills with standers; authored events stay for the shift.

Docs and tests
- PLAN.md test/CI section corrected to the custom headless runner and Gitea Actions.
- README controls table, smoke checklist, test count, and status lists refreshed.
- TODO/DONE/MEMORY updated; completed sections moved to DONE.md.
- Headless suite 77 -> 88 passing (settings round-trip, step colliders, skyline
  alpha, session-shell UI behavior, traffic lifetime).

TODO.md

@@ -1,39 +1,12 @@
 # TODO
 
 Godot 4.3 prototype. Release **v0.2.1** is live on the host. The working tree (uncommitted)
-has the access-loadout fix and the ADR-0007–0010 control pass; headless suite **77/77** and a
-windowed focus/radial smoke pass.
+has the access-loadout fix, the ADR-0007–0010 control pass, and the session-shell / world
+follow-up batch; headless suite **88/88**, plus `smoke_session_shell.gd` and the windowed
+focus/radial smoke.
 
 Host `REQUIRE_SIGNIN_VIEW` stays deferred.
 
-## World and presentation follow-ups (found during the control smoke)
-
-- [ ] The skyline backdrop was removed: `assets/textures/ai/game_ready/skyline.png` has an
-      opaque black background, so the planes rendered as black slabs with window dots. Re-add
-      the backdrop only with a transparent asset or a keyed shader.
-- [ ] Guard settles ~0.5 m above the ground after spawning on the landing. Check the capsule
-      offset and the spawn `y`, and verify eye height while walking the steps.
-- [ ] Steps and the landing are visual-only (no collider). The guard walks through them; add
-      simple step colliders or restage the landing so it does not intersect the walk path.
-- [ ] Marquee text (`STEP LINE`) is tiny from the sidewalk. Scale the Label3D up.
-- [ ] Focus ring and name tag are small at 2–3 m. Consider a larger torus / font after a
-      real playtest.
-- [ ] NPC crowd cap (`MAX_LIVE_NPCS`) silently drops routine traffic at 16. Add a short
-      despawn/lifetime for ordinary guests so the entrance does not fill up with standers.
-
-## Session shell
-
-The game boots into a live 900 s shift. `Save` declares `settings.json` and never uses it.
-`V` cycles venues by restarting the shift.
-
-- [ ] Startup menu: pick venue, start shift, quit. Keyboard + click. Replaces `V` as the
-      player-facing path (`V` may stay as a debug bind).
-- [ ] Pause overlay when `Esc` releases the mouse (or a dedicated pause key): resume, restart
-      shift, settings, quit to menu.
-- [ ] Settings: mouse look sensitivity, persist through `Save` / `settings.json`. Load on boot.
-- [ ] Shift review "Run another shift" returns to the venue menu, not a silent restart of the
-      same scenario.
-
 ## Remaining PLAN verbs (radial exists)
 
 - [ ] Eye contact as a Level 1 action (PLAN / glossary). Distinct from raise-hand. Add a
@@ -101,14 +74,6 @@ is in the working tree. Bodies still idle-stand at those spots.
 - [ ] Building: "activate body camera" and "request reason" once those verbs exist, used in
       at least one authored event.
 
-## Documentation drift
-
-- [x] README controls table, smoke checklist, test count, and implemented/not-yet lists
-      refreshed for the control pass (77 tests).
-- [ ] `PLAN.md` Tech Stack / Planned Commands still say GUT and GitHub Actions; the project
-      uses `src/test/test_runner.gd` and `.gitea/workflows/build.yml`.
-- [x] MEMORY: door_staff_lines log through `GameManager`; 300 s default removed.
-
 ## Distribution follow-up (host config, deferred)
 
 Verified via API+host credentials (2026-10-31):