fix: refimpl hash format aligned to -01 spec, draft rebuilt

Updated Go ValidateHashFormat to plain base64url (no algorithm prefix)
per -01 spec and RFC 9449. Python already fixed. All tests pass.

docs/status.md

@@ -1,5 +1,35 @@
 # research.ietf — Status
 
+## 2026-04-11 — Refimpl -01 hash format fix + draft rebuild
+
+### What was done
+
+1. **Go `ValidateHashFormat` updated to -01 spec**: Was still validating old `algorithm:base64url` format (e.g. `sha-256:abc...`). Now validates plain base64url without prefix, matching -01 spec and RFC 9449.
+2. **Go `ErrHashFormat` error message updated** to match new format.
+3. **IMPROVEMENTS.md updated**: Section 5 and section 6 hash format entries corrected.
+4. **Draft rebuilt**: `build.sh` run with `kramdown-rfc2629` (freshly installed) and `xml2rfc`. XML/TXT/HTML regenerated.
+5. **All tests pass**: Python (56 tests, 90% coverage), Go (all pass).
+
+### Claim name migration summary (-00 to -01)
+
+All claim name changes were already implemented in core library code (types, create, verify, dag) for both Go and Python:
+
+| Change | Status |
+|--------|--------|
+| `par` -> `pred` | Done (both) |
+| `pol`/`pol_decision` removed from core, moved to `ect_ext` | Done (both) |
+| `sub` removed | Done (both) |
+| `typ: wimse-exec+jwt` -> `exec+jwt` (preferred) | Done (both) |
+| `MaxParLength` -> `MaxPredLength` | Done (both) |
+| Hash format: `algorithm:base64url` -> plain base64url | **Fixed in this session** (Go was still using old format) |
+
+### Remaining items (not claim name changes)
+
+- L1 support (unsigned JSON ECTs) — not yet implemented
+- L3 support (audit ledger hash chain + receipts) — not yet implemented
+
+---
+
 ## 2026-04-03 — Draft Assessment and Cleanup
 
 ### Current State