docs(changelog): record the BlastMate serial fix under v0.29.0

The release is bumped but not tagged, and the fix is now in dev — which is
what gets built — so the notes would otherwise understate the build. No
TOOL_VERSION change: the fix alters which serial an import is filed under,
not any decoded value, so no backfill is owed.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HgTe8CamXAHcAmaQ6QNcog

CHANGELOG.md

@@ -25,6 +25,32 @@ on startup; the offset detector still needs the shape backfill on the prod store
   rebuild); exposed via `/db/events`. Terra-View surfaces it as a manual
   "Flag as offset" action + an `FT · offset` badge.
 
+### Fixed
+- **BlastMate serials — the family prefix is read from the file, not guessed.**
+  The Blastware filename encodes only the serial *number* (`L895…` → 10895);
+  the two-letter prefix is not in it. `waveform_store` synthesised `"BE"`, so
+  an imported **BlastMate** (serials `BA…`) was filed under a MiniMate Plus
+  serial that does not exist — silently, and Terra-View read it straight
+  through. `save_imported_bw` now resolves serial as hint → file body →
+  filename guess, via a new `_serial_from_bw_bytes` that accepts a candidate
+  only when its numeric part matches the filename. `client._decode_0a_partial_header`
+  likewise matched a literal `b"BE"` in monitor-log partial records; on a
+  BlastMate that returned −1 and skipped the whole block, losing the **geo
+  threshold** along with the serial. It now matches any two-letter prefix and
+  requires the NUL terminator — stricter than the search it replaces.
+
+  BlastMate is the MiniMate Plus's larger Series III sibling and its files are
+  byte-compatible: all 1,493 in the DL2 archive decode through the existing
+  codec at 100%, same four channels. **The serial string was the only thing
+  blocking BlastMate support in SFM.** Four archive units were affected —
+  BA9229, BA10060, BA10895, BA15957.
+
+  **No backfill and no `TOOL_VERSION` bump**: this changes which serial an
+  *import* is filed under, not any decoded value, so existing sidecars and
+  `.h5` files are untouched. **No migration either** — prod holds no BlastMate
+  events (the archive's BA units last recorded 2018-10 through 2023-11; the
+  prod backfill reaches back only to ~May 2025).
+
 ---
 
 ## v0.28.0 — 2026-09-02