Reduce noisy Gemini partial failure counts

TODO.md

@@ -235,6 +235,7 @@
 - Artgrid preview playback now has a server-side ffmpeg transcode path for `.m3u8` style preview URLs, but this trades storage savings for runtime CPU cost.
 - The provided Artgrid HTML sample still does not expose a direct preview `m3u8` or `mp4` URL by itself, and `yt-dlp` probe on the sample clip URL returned `Unsupported URL`, so fully reliable Artgrid playback still depends on live-page/runtime preview discovery succeeding elsewhere in the pipeline.
 - Docker CLI is not installed in this environment, so container-image build verification still cannot be performed locally from this machine.
+- Gemini batch warnings can still mix true model/output failures with harmless candidate-skip cases unless the recovery path filters those error classes before surfacing them.
 - The local self-test script is better than before, but it is still a smoke test, not full integration coverage.
 
 ## Current Risks Around Search Quality
@@ -557,6 +558,7 @@
 - [ ] Reduce `/api/search` latency further without collapsing result count
 - [ ] Rebuild the reverted search-expansion work from the previous stable baseline, but only after measuring where candidate quality collapses between ranked pool and final merge
 - [ ] Validate the reopened `5ca7aef` search-breadth direction against real proxy timeouts and visible result count before widening it any further
+- [ ] Continue hardening Gemini batch parsing so truncated JSON and ignorable low-visual candidate failures do not inflate user-facing warning counts
 - [ ] Build a repeatable repo-local bootstrap script or documented setup command set for non-root machines so fresh PC setup does not depend on shell history
 - [ ] Improve Envato / Artgrid preview acquisition reliability so Gemini Vision sees real frames more often
 - [ ] Browser-verify the new result modal at multiple viewport heights and confirm translated Source Summary readability on real long descriptions
@@ -628,6 +630,24 @@
 - If behavior in the browser does not match the latest backend/frontend code, the first assumption should be stale frontend assets until proven otherwise
 
 ## Recent Change Log
+- Date: `2026-03-17`
+- What changed:
+  - Restored hard/ignorable Gemini batch error filtering so low-value thumbnail skips and no-visual candidate skips do not count as user-facing partial batch failures when useful recommendations were still recovered.
+  - Added unit coverage for the Gemini batch error filtering behavior.
+- Why it changed:
+  - The user reported the warning `gemini vision partially failed on 3 of 4 batches`.
+  - The provided log `ai-media-hub-2026-03-17T06-06-04-447Z.log` showed three different batch-failure classes mixed together:
+    - real Gemini JSON extraction failures
+    - low-value thumbnail skips
+    - no-visual candidate skips
+  - Only the first class should strongly influence the user-facing partial-failure warning.
+- How it was verified:
+  - `go test ./...`
+  - `bash scripts/selftest.sh`
+- What is still risky or incomplete:
+  - This reduces noisy partial-failure warnings, but it does not eliminate genuine Gemini JSON truncation or provider-side preview problems.
+  - If the model starts returning different malformed JSON patterns, the parser and warning logic may still need further hardening.
+
 - Date: `2026-03-17`
 - What changed:
   - Reapplied the broader-search / modal-fitting codepath from `5ca7aef` as requested by the user.