docs: align tracked files to single coherent SoT

Contradictions resolved:

- AGENTS.md: add 'Known stale PRD lines' section (FR17, FR19, FR40, NFR, FR42)
  so PRD's cross-reference resolves
- AGENTS §6: remove 'tag sets' from Call 1 body description (Call 1 only uses
  species and attribute lists)
- PROMPTS.md: shipped defaults path corrected to backend/app/prompts/ (matches
  DEPLOYMENT repo layout)
- PROMPTS.md: Call 1 notes removed feat-* and fig-* from taxonomy list (Call 1
  returns free-text observations mapped to feat-* tags by server, not fig-*)
- PROMPTS.md: Call 2 template field names aligned with CONTENT-WOO defaults
  (width_avg_in, width_min_in, width_max_in, length_in_remainder)
- UX.md §112: remove 'tag lists' from Call 1 body description
- DATA-MODEL: prompt files location corrected from /data/prompts/ to
  backend/app/prompts/ (bind-mounted read-only to /app/prompts/)
- DEPLOYMENT: backup script updated (prompts are version-controlled in repo,
  no separate backup needed)
- docker-compose.yml: prompts mount corrected to ../backend/app/prompts

docs/DEPLOYMENT.md

@@ -147,11 +147,14 @@ provide `python -m app.security.rekey NEW_KEY` (reads old key from env
 ```
 1. sqlite3 /data/slab.db ".backup /backups/slab-YYYYMMDD.db"   # WAL-safe
 2. tar czf /backups/slab-images-YYYYMMDD.tgz -C /images .
-3. cp -r /backups/prompts-YYYYMMDD.tar.gz prompts/              # prompt files
-4. retain: 7 daily + 4 weekly; prune older
-5. log result to /var/log/slab-backup.log; alert (Hermes) on failure
+3. retain: 7 daily + 4 weekly; prune older
+4. log result to /var/log/slab-backup.log; alert (Hermes) on failure
 ```
 
+Prompt files live in the git repo (`backend/app/prompts/`) and are version-controlled;
+they do not need a separate backup. The `reset-to-default` script restores shipped
+defaults from the app bundle.
+
 - Backup target: local dir first; mirror to an off-box share for safety (same pattern
   as other stacks on the host).
 - **Restore**: stop compose → restore DB file + untar images → start compose.