chore(release): v0.27.0 — decoder verified at scale; offset investigation

Bumps pyproject, TOOL_VERSION, README and CLAUDE.md to 0.27.0. sfm/server.py
now derives its version from TOOL_VERSION (c8c4ec2), so that constant is the
single source of truth for the service version and the sidecar stamp alike.

What ships:
  - histogram partial-final-block fix (4 files recovered, 0 regressed)
  - interval-based find_twins matching (terra-view #102 sub-task 2)
  - /health no longer reports a hard-coded 0.1.0
  - 793 NUL bytes stripped from CLAUDE.md (made grep skip it as binary)
  - docs/offset_investigation.md, and the offset detectors
  - scratch/verify_against_ascii.py

Verification: the series-3 codec now decodes 14,338 / 14,338 archive pairs
exactly against their Blastware ASCII exports (1,249 waveform + 13,089
histogram, 45 units, back to 2018) — 11x the ground truth the prod store
carried, and it supersedes the old "per-sample on 11% of files" caveat.

Independent check on the scale: 19,244 healthy channel-events sit at a
pre-trigger floor of exactly 0.000 (62.7%), 94.5% within one quantisation
unit, median +0.0000. No zero-point bias in the decoder.

⚠ TOOL_VERSION moved, so the next prod backfill regenerates the whole store
(~2 hours on the NAS). That is intended — it is what publishes the 4 recovered
histograms — but it is not a no-op; schedule it.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HgTe8CamXAHcAmaQ6QNcog

minimateplus/event_file_io.py

@@ -50,7 +50,7 @@ SIDECAR_KIND   = "sfm.event"
 # bumped without a `pip install` re-run — leading to confusing stale
 # version stamps in sidecars.  Bump this constant and CHANGELOG.md
 # together at release time.
-TOOL_VERSION = "0.26.0"
+TOOL_VERSION = "0.27.0"
 
 try:
     # Best-effort: prefer the installed metadata when it's NEWER than the