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/smoke.qa.spec.ts

@@ -24,7 +24,7 @@ import {
 test("image: resize round-trip, previews, dimension oracle", async ({ page }) => {
   const issues = instrument(page);
   await gotoTool(page, "resize");
-  await uploadFiles(page, fixture("formats", "sample.png"));
+  await uploadFiles(page, fixture("image", "formats", "sample.png"));
   await assertNoBrokenImages(page);
   await page.locator("#resize-width").fill("64");
   const res = await processTool(page, "resize", "fast");
@@ -39,7 +39,7 @@ test("image: resize round-trip, previews, dimension oracle", async ({ page }) =>
 
 test("image: convert png -> webp, magic-byte oracle", async ({ page }) => {
   await gotoTool(page, "convert");
-  await uploadFiles(page, fixture("formats", "sample.png"));
+  await uploadFiles(page, fixture("image", "formats", "sample.png"));
   await assertNoBrokenImages(page);
   await page.locator("#convert-target-format").selectOption("webp");
   const res = await processTool(page, "convert", "fast");
@@ -50,18 +50,18 @@ test("image: convert png -> webp, magic-byte oracle", async ({ page }) => {
 
 test("video: input preview decodes (tiny.mp4)", async ({ page }) => {
   await gotoTool(page, "convert-video");
-  await uploadFiles(page, fixture("media", "tiny.mp4"));
+  await uploadFiles(page, fixture("video", "formats", "tiny.mp4"));
   await assertVideoPreview(page);
 });
 
 test("audio: input waveform ready (tiny.mp3)", async ({ page }) => {
   await gotoTool(page, "convert-audio");
-  await uploadFiles(page, fixture("media", "tiny.mp3"));
+  await uploadFiles(page, fixture("audio", "formats", "tiny.mp3"));
   await assertAudioPreview(page);
 });
 
 test("document: pdf input preview renders (tiny.pdf)", async ({ page }) => {
   await gotoTool(page, "rotate-pdf");
-  await uploadFiles(page, fixture("documents", "tiny.pdf"));
+  await uploadFiles(page, fixture("document", "formats", "tiny.pdf"));
   await assertDocumentPreview(page);
 });