series 4 codec work, inital decode success

CLAUDE.md

@@ -73,6 +73,28 @@ should not import from `sfm/`, must not touch a DB, and have no I/O
 beyond reading files passed as arguments.  Keep them pure — both
 tiers can then depend on them without circularity.
 
+#### Thor IDF binary codec (2026-05-28)
+
+`micromate/idf_file.read_idf_file()` decodes both Thor IDFW
+(waveform) and IDFH (histogram) binaries.
+
+- **IDFW** reuses `decode_waveform_v2()` on the body at fixed file
+  offset `0x0f1f`.  Sample fidelity is 87–99% byte-exact on quiet
+  events; loud events hit the BW codec's known walker-stops-early
+  limitation.
+- **IDFH** has its own segment-based decoder: `[len_be][0a 00 00 00]
+  [00 NN][05 3f]` + N × 72-byte interval records (4 × 16-byte
+  per-channel min/max/halfp).  All 859 Thor IDFH corpus files
+  decode (181,071 intervals); peak matches sidecar within ~1.8%
+  (ADC quantization).
+
+The two outlier `BE9439_*` files in the Thor example corpus are
+actually Series III Blastware binaries that share the `.IDFW`/`.IDFH`
+filename convention by accident.  `read_idf_file()` detects them by
+their BW STRT signature and raises NotImplementedError pointing
+callers at `read_blastware_file()`.  See
+`docs/idf_protocol_reference.md` for full field layouts.
+
 ### Practical consequences
 
 When deciding where new code goes, ask: