Revert "Harden single-candidate gemini recovery"

This reverts commit b6a217cab9.

TODO.md

@@ -655,24 +655,6 @@
 - 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:
-  - Added a dedicated single-candidate Gemini recovery path that no longer asks for JSON and instead parses a tiny plain-text key/value response.
-  - Kept multi-candidate Gemini Vision on compact JSON, but changed sequential recovery to use the shorter plain-text format automatically through the existing `Recommend(..., []SearchResult{item})` path.
-  - Added unit coverage for the single-candidate plain-text parser.
-- Why it changed:
-  - The user-provided log `ai-media-hub-2026-03-17T08-20-31-074Z.log` showed even more severe truncation:
-    - `"{\"recommendations\":[{\"index\":"`
-    - `"{\"recommendations"`
-    - `"{\"recommend"`
-  - The same log showed `sequentialRetried: 0`, which means the old single-candidate recovery path was still too verbose and was not successfully rescuing failed batches.
-- How it was verified:
-  - `pwsh -NoProfile -File scripts/selftest.ps1`
-  - added Go tests for single-candidate Gemini plain-text parsing
-- What is still risky or incomplete:
-  - If Gemini returns malformed plain text that omits the required `verdict:` line, even the single-candidate recovery path can still fail.
-  - This improves recovery robustness, but total Gemini latency can still rise when many batch failures fall back to candidate-by-candidate evaluation.
-
 - Date: `2026-03-17`
 - What changed:
   - Added adaptive Gemini Vision output-token sizing so smaller candidate batches, especially single-candidate sequential recovery calls, now request much shorter responses.