docs: refresh stale version/test-count/locale numbers

- Version stamps v0.51.192/v0.50.281 → v0.51.792 (Jul 1) in the factual
  header lines (ROADMAP/ARCHITECTURE/SPRINTS/TESTING); curated narrative
  left untouched
- Test counts: the ~7,150 approximates and leftover absolute 5303/488 and
  3995 figures → ~11,500 tests / ~1,150 files (matches --collect-only)
- Locales: 9 → 14 (add Italian, Turkish, Polish, Vietnamese) in ROADMAP;
  '11 languages' → 14 in TESTING

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

SPRINTS.md

@@ -2,7 +2,7 @@
 
 > Forward-looking sprint plan and active queue.
 >
-> Current state: v0.50.281 | 3995 tests | port 8787
+> Current state: v0.51.792 | ~11,500 tests | port 8787
 > Target A (CLI parity): ✅ Complete
 > Target B (Claude parity): ~95% — full subagent transparency UI and code-execution cells remain
 >