fix: repair docker validation QA tooling, dispatcher crash-accounting, and image-enhancement RAW hang (#391)

Found and fixed during a full local Docker build validation (amd64/arm64, all
four fleet targets, AI bundle installs, QA harness) and the follow-up bug
sweep requested afterward. None of the affected scripts run in CI, so these
had been silently broken indefinitely.

- docker/feature-manifest.json: pythonVersion was a flat "3.11", but the
  amd64 base (Ubuntu 24.04) ships Python 3.12 while arm64 (Debian bookworm)
  ships 3.11. Changed to a per-arch object matching the file's existing
  convention.
- tests/qa/api-sweep.mts and verify-ai.mts: bare "@snapotter/shared" import
  can't resolve since tests/ is not a pnpm workspace member, making both
  silently unrunnable via their own documented command on any fresh
  checkout. Switched to a relative import.
- tests/qa/generate-ledger.mts: wrote to docs/qa/ without creating the
  directory first; docs/ is gitignored except COMMUNITY_GUIDE.md, so a fresh
  checkout threw ENOENT.
- Seven QA Playwright spec files (input-preview, settings,
  settings-extended, multifile, output-preview, pipeline-ui, smoke) had
  ~115 fixture() calls using directory names that don't exist. Resolved
  every call programmatically against the real fixture tree.
- packages/ai/src/bridge.ts: AI dispatcher restart (happens on every bundle
  install) was falsely counted as a crash, risking permanent dispatcher
  disable after enough legitimate restarts within the crash window. Added a
  shuttingDown flag checked at all three recordCrash() call sites.
- packages/image-engine/src/operations/auto-enhance.ts: image-enhancement
  hung 40+ seconds on large RAW photos (confirmed on a real 20.2MP file) in
  Sharp's .clahe() step, whose cost scales with total pixel count regardless
  of tile size. Added a 16-megapixel cap above which CLAHE is skipped;
  verified against the real file (40+s -> 2.0s) with no regression to other
  RAW formats or normal-sized images. Fixing this surfaced a second,
  smaller bug where the saturation step's CLAHE compensation boost was
  keyed off the raw toggle instead of whether CLAHE actually ran.
- Two QA-harness robustness gaps closed per "fix everything, even the small
  bugs": the passport-photo/erase-object input-preview tests now skip
  cleanly with a clear reason on a container without their AI bundle
  installed, and docker-compose.qa.yml's hardcoded project/container name
  (the actual root cause of a mid-validation container swap between two
  concurrent sessions) is now parameterized via QA_PROJECT_NAME.

Full validation report is local-only per repo convention.

tests/qa/docker-compose.qa.yml

@@ -4,12 +4,18 @@
 # clashing with a native dev server on 1349.
 #   docker compose -f tests/qa/docker-compose.qa.yml up -d
 #   open http://localhost:13499
-name: snapotter-qa
+#
+# Project/container names default to snapotter-qa. Two sessions on the same host
+# running this file verbatim at the same time will silently steal each other's
+# container (last `up` wins, no error) since container_name is fixed rather than
+# derived from the project name. If you need a second concurrent stack, override:
+#   QA_PROJECT_NAME=snapotter-qa-2 docker compose -f tests/qa/docker-compose.qa.yml up -d
+name: ${QA_PROJECT_NAME:-snapotter-qa}
 
 services:
   app:
     image: snapotter/snapotter:latest
-    container_name: snapotter-qa
+    container_name: ${QA_PROJECT_NAME:-snapotter-qa}
     ports:
       - "13499:1349"
     volumes:
@@ -45,7 +51,7 @@ services:
 
   postgres:
     image: postgres:17-alpine
-    container_name: snapotter-qa-postgres
+    container_name: ${QA_PROJECT_NAME:-snapotter-qa}-postgres
     environment:
       POSTGRES_USER: snapotter
       POSTGRES_PASSWORD: snapotter
@@ -61,7 +67,7 @@ services:
 
   redis:
     image: redis:8-alpine
-    container_name: snapotter-qa-redis
+    container_name: ${QA_PROJECT_NAME:-snapotter-qa}-redis
     command: ["redis-server", "--maxmemory-policy", "noeviction", "--appendonly", "yes"]
     volumes:
       - qa-redisdata:/data