Extract reports unidentifiable boxes for human retakes

The vision prompt now returns {titles, unidentified}: boxes that look
like games but can't be confidently titled are reported (location
relative to identified neighbors, partial text, art notes) instead of
silently omitted. They land in data/unidentified.json keyed by photo,
and the end-of-run summary lists them — plus low-confidence reads —
with instructions to retake a closer photo and re-run. New --force flag
re-extracts everything; pre-feature raw caches (bare arrays) still
parse. Live run on IMG_4499 confirmed the flow and the low-confidence
list correctly flags the known "Hebarceos" misread.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

bgg-shelf-pipeline-spec.md

@@ -45,6 +45,7 @@ Each stage reads the previous stage's artifact and writes its own. Re-running a
 - Output: `titles.json` — list of `{title_raw, title_normalized, confidence, publisher_hint, edition_hint, year_hint, language_hint, art_notes, source_photos[]}`.
 - Dedupe nuance: identical normalized titles from different photos collapse to one entry ONLY if their edition cues don't conflict; conflicting cues (different publisher/edition text) stay as separate entries.
 - Support `--only <photo>` to re-run a single photo (e.g., after retaking a blurry shot).
+- **Unidentified sightings**: boxes that appear to be games but can't be confidently titled (blurry, obscured, sharp angle, frame edge) are reported rather than silently omitted — location described relative to identified neighbors, plus any partial text and art notes → `unidentified.json`, keyed by photo. The end-of-run summary lists them (and low-confidence reads) so I can take a closer photo and re-run with `--only`.
 
 ### Stage 2 — `resolve`: Match titles to BGG IDs
 
@@ -104,6 +105,7 @@ Each stage reads the previous stage's artifact and writes its own. Re-running a
 All artifacts are flat files in a `data/` directory — human-readable, git-friendly, and reusable by the future frontend:
 
 - `titles.json` — extraction output (stage 1)
+- `unidentified.json` — game boxes seen but not identified (stage 1); retake prompts
 - `bgg_cache/` — cached XML API responses
 - `matches.csv` — the master matching table (stages 2–3)
 - `to_add.csv` — upload queue, new entries (stage 4)