art(review): local review app -- persistent verdicts + notes, multi-session (serve_review.py) (#706)

Adds tools/art_review/serve_review.py: a stdlib-only (http.server, no deps) local
web app that reviews ALL P(Doom)1 art in one place -- pixellab art_source/ AND the
gpt-image art_generated/ tree (game_icons, ui_icons, hero_banners,
screen_backgrounds, terminal_textures, + any new category dirs).

Per asset: clickable keep/maybe/reroll verdict, free-text note, comma tags, on a
checkered alpha backdrop, grouped by category with a sticky section nav and
keyboard nav (arrows / K / M / R / N). Every edit POSTs to /api/state and
AUTO-PERSISTS to tools/art_review/review_state.json on disk (not localStorage), so
a review survives across sittings and is a clean pipeline input:
  { asset_id: { verdict, note, tags, updated_at } }
asset_id is pipeline-friendly: gen:<category>:<base_id>:<variant> / px:<relpath>.

PNGs stream live from disk via /img?p=<relpath> (path-sandboxed to art-root, png
only) -- the 1.1 GB gitignored art_generated/ tree is never copied or committed.
Closes the "build.py doesn't read art_generated" glue gap in ASSET_PIPELINE.md.

review_state.json is gitignored (per-reviewer local state).

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

Author: PipFoweraker

.gitignore

@@ -130,6 +130,8 @@ test-results-*.xml
 art_generated/
 generated_icons/
 asset_gallery.html
+# Local art-review app state (per-reviewer verdicts/notes; written by serve_review.py)
+tools/art_review/review_state.json
 test_output.png
 test_openai_api.py
 generate_icons.py