chore: v1-prep hygiene sweep — LICENSE (MIT), fixtures under tools/, doc staleness

Three-way audit ahead of v1 (structure/necessity, docs-vs-code drift,
mechanical checkers) came back clean: zero dead files, zero doc hard
errors, all 92 options documented, all consistency checkers green, no
untracked files. What it did surface, fixed here:

- LICENSE was missing entirely — the one hard launch blocker. MIT
  (Bernardo's call), pointer at the README foot.
- checks/ was the only top-level dir outside the documented layout rule;
  its two state-legacy-name fixtures moved to tools/fixtures/ (Bernardo
  chose move over documenting an exception), flake.nix refs + drift
  messages updated.
- Doc staleness: two leftover "theme-state" leads (HARDWARE.md,
  REQUIREMENTS.md) now say state.json; VISION Theme C charge-limit row
  gets its ✓; VISION agent-slices datestamp bumped.
- The idle.nix miniTransition duplication (same binary name, lossy
  subset of the real display-transition tool) is deliberately NOT
  refactored here — filed as PROPOSED #150 with the audit evidence.

Wallpapers-in-repo (97 MB) is the known LATER artifact-split item, not
re-filed.

Verification: V0 — nix flake check --no-build green after the fixture
move (state-legacy-name's eval asserts exercise the new paths); doc
edits prose-reviewed. Audits by three Sonnet passes; triage on Fable.

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

README.md

@@ -542,3 +542,5 @@ reload                          # exec zsh (reload the shell)
 | **[agent/LOOP.md](agent/LOOP.md)** | Autonomous iteration protocol |
 
 Kept out of the README body so this stays a focused entry point.
+
+License: [MIT](LICENSE).