docs: close BUG-16 (fixed + verified), update Phase 29 status

PLAN.md

@@ -2267,8 +2267,16 @@ The app reuses the existing Pi REST API surface with no changes:
 **Owner completed a second road test on 2026-08-13.** Issues found during the drive are
 logged as `BUG-XX` entries in [BUGS.md](./BUGS.md) (BUG-16 onward) and fixed + verified here.
 
+- **BUG-16 (trip missing from Pi local history) — ✅ FIXED**: `connect_obd()` set
+  `_car_ever_connected` without a `global` declaration, so the module-level flag was never
+  set and local trip building was silently blocked since BUG-10. The flag is now persisted
+  across reboots; also fixed a NULL-GPS speed-only row crash in the trip builder. Verified the
+  2026-08-13 drive now appears locally.
+- **BUG-17 (trip timestamps wrong) — OPEN**: no RTC → clock drifts without internet.
+- **BUG-18 (no RTC) — OPEN**: add a battery-backed RTC (DS3231) / GNSS time source.
+
 Open items from the drive — fill in as reported:
-- (none yet)
+- BUG-17 / BUG-18 (clock) pending.
 
 ## Working Notes / Environment Gotchas