feat(state): opt-in auto-commit of state mutations (Phase 4)

settings.autoCommit — toggled from System › Auto-commit (self-gated on
the flake being a git repo) — makes every nomarchy-theme-sync apply/set
also git-commit theme-state.json in the downstream flake, so settings
history is `git log`. Off by default.

Design: the flag is live-read by the tool on each write (nothing in Nix
consumes it → instant toggle, no rebuild, no new option); the commit is
pathspec-limited to theme-state.json so unrelated dirty files are never
swept up; it fires when the flag is on before OR after the write, so
the disable-toggle itself lands in history; same-value writes no-op
(diff against HEAD); missing git identity falls back to
Nomarchy <nomarchy@localhost>; `bg next` is deliberately excluded.

Rider fix: `get` now prints booleans JSON-style (true, not Python's
True) — un-sticking the System menu's "Auto timezone (on/off)" label,
whose `= true` comparison could never match. All shell consumers
already normalise true|True, so no other behavior change.

Verified: V0 (py_compile, nix flake check) + V1 (HM generation builds,
generated nomarchy-menu passes bash -n, wiring present in the rendered
script) + a 7-assertion sandbox-repo round-trip covering enable/set/
same-value/disable/post-disable/apply paths and the identity fallback.
Remaining: on-machine check queued in agent/HARDWARE-QUEUE.md.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

agent/HARDWARE-QUEUE.md

@@ -43,6 +43,12 @@ QA machine), the **T14s** (webcam case).
 - [ ] **Visual theme pass** — live ISO: all six identity themes (bars) +
       the four authored rofi `.rasi` (nord/retro-82/lumon/kanagawa) look
       right, not just parse.
+- [ ] **Auto-commit on a real machine** — System › Auto-commit toggles on
+      (row shows state, notification fires); a theme apply from SUPER+T then
+      shows a `nomarchy: apply theme …` commit in `~/.nomarchy` (`git log`);
+      unrelated dirty files in the checkout stay uncommitted; toggle off is
+      itself the last commit. Also: the "Auto timezone (on/off)" row label
+      now reflects the real state (the `= true` comparison fix).
 
 ## AMD dev box only
 - [ ] **AMD runtime bits** — VA-API (`vainfo` → radeonsi), amd-pstate EPP