feat: migrate refimpls from draft-00 to draft-01 claim names

- Rename `par` to `pred` (predecessor) in types, serialization, tests
- Remove `pol`, `pol_decision` from core payload; move to `ect_ext`
- Remove `sub` from payload (not part of ECT spec)
- Update `typ` from `wimse-exec+jwt` to `exec+jwt` (accept both)
- Rename MaxParLength to MaxPredLength everywhere
- Update testdata, demos, READMEs with migration table
- All Go tests pass, all 56 Python tests pass (90% coverage)

refimpl/go-lang/README.md

@@ -1,6 +1,6 @@
 # WIMSE ECT — Go Reference Implementation
 
-Go reference implementation of [Execution Context Tokens (ECTs)](../../draft-nennemann-wimse-execution-context-00.txt) for WIMSE. Implements ECT creation (ES256), verification (Section 7), DAG validation (Section 6), and an in-memory audit ledger (Section 9).
+Go reference implementation of [Execution Context Tokens (ECTs)](../../draft-nennemann-wimse-execution-context-01.txt) for WIMSE. Implements ECT creation (ES256), verification (Section 7), DAG validation (Section 6), and an in-memory audit ledger (Section 9).
 
 ## Layout
 
@@ -43,9 +43,11 @@ payload := &ect.Payload{
     Exp: time.Now().Add(10*time.Minute).Unix(),
     Jti: "550e8400-e29b-41d4-a716-446655440000",
     ExecAct: "review_spec",
-    Par: []string{},
-    Pol: "policy_v1",
-    PolDecision: ect.PolDecisionApproved,
+    Pred: []string{},
+    Ext: map[string]interface{}{
+        "pol": "policy_v1",
+        "pol_decision": "approved",
+    },
 }
 compact, err := ect.Create(payload, key, cfg.CreateOptions("agent-a-key"))
 
@@ -84,6 +86,16 @@ cd refimpl/go-lang && go test ./ect/... -cover
 
 Unit tests are in `ect/*_test.go`. Coverage target: **~90%** (run `go test ./ect/... -coverprofile=cover.out && go tool cover -func=cover.out`). Remaining uncovered lines are mostly Parse/Verify error paths that require custom JWS or multi-sig tokens.
 
+## draft-01 claim changes
+
+| -00 (previous) | -01 (current) | Notes |
+|----------------|---------------|-------|
+| `par`          | `pred`        | Predecessor task IDs |
+| `pol`, `pol_decision` | removed (use `ect_ext`) | Policy claims moved to extension object |
+| `sub`          | not defined   | Standard JWT claim, not part of ECT spec |
+| `typ: wimse-exec+jwt` | `typ: exec+jwt` (preferred) | Both accepted for backward compat |
+| `MaxParLength` | `MaxPredLength` | Renamed to match `pred` claim |
+
 ## Production configuration (environment)
 
 | Variable | Default | Description |
@@ -96,7 +108,7 @@ Unit tests are in `ect/*_test.go`. Coverage target: **~90%** (run `go test ./ect
 
 ### Replay cache (multi-instance)
 
-`JTICache` is in-memory only. For multiple verifier instances (e.g. behind a load balancer), use a shared store (Redis, database) so every instance sees the same “seen” JTIs. Implement `JTISeen` as a function that checks (and optionally records) the JTI in that store (e.g. with TTL). Pass it in `VerifyOptions.JTISeen`. See refimpl/README for an overview.
+`JTICache` is in-memory only. For multiple verifier instances (e.g. behind a load balancer), use a shared store (Redis, database) so every instance sees the same "seen" JTIs. Implement `JTISeen` as a function that checks (and optionally records) the JTI in that store (e.g. with TTL). Pass it in `VerifyOptions.JTISeen`. See refimpl/README for an overview.
 
 ## Dependencies