checkpoint: bug-851 root cause + raft TLA+ conformance spec family

Investigation & fixes (failover committed-job loss):
- root-cause bug-851 on an owned 3-node cluster: chaotic failover causes
  silent committed-prefix divergence (WAL hdr.term always 0; two leaders
  per term; no (term,lsn) reconcile). Evidence in repro-851/ + INVESTIGATION.
- live-validated fixes 848/849/850 (recovery-on-promotion, advertise real
  applied_lsn, persist-layer contiguity guard); add waldump WAL inspector.

Specs (strict raft.tla conformance — library owns the log):
- TLA-gap-analysis.md: impl vs raft/raft.tla, gaps G1-G6.
- raft-log-replication, raft-commit-safety, raft-sim-conformance: extend
  src/lib/raft to own log/commit/verification via callbacks (specs generated,
  cross-spec review passed).
- ha-term-safety: controller-side adapter + config marker (R1-R7); design done.
- config-upgrade-snapshot: R8 descoped here (deps entity-bearing-snapshots, bug-857).
- roadmap + buglog (851/854/857) + .wolf knowledge updated.

.kiro/specs/raft-sim-conformance/spec.json

@@ -0,0 +1,23 @@
+{
+  "feature_name": "raft-sim-conformance",
+  "created_at": "2026-06-21T13:00:00Z",
+  "updated_at": "2026-06-21T13:00:00Z",
+  "language": "en",
+  "phase": "tasks-generated",
+  "approvals": {
+    "requirements": {
+      "generated": true,
+      "approved": true
+    },
+    "design": {
+      "generated": true,
+      "approved": true
+    },
+    "tasks": {
+      "generated": true,
+      "approved": true
+    }
+  },
+  "ready_for_implementation": true,
+  "note": "Auto-approved (-y mode). Extends src/lib/raft/raft_sim.c into an in-process TLA+ conformance/verification harness driving N library instances through raft.tla Next-action-equivalent transitions (Restart, Timeout, RequestVote, BecomeLeader, ClientRequest, AppendEntries, AdvanceCommitIndex, Receive incl. UpdateTerm + DropStaleResponse, DuplicateMessage, DropMessage) and asserting the four Raft safety invariants (Election Safety, Log Matching, Leader Completeness, State Machine Safety) every step. Seedable/deterministic driver; randomized + targeted scenarios (partitions, restarts, drop/dup/reorder, Figure-8); failure-trace reproduction; CI-runnable target; deliberately-broken-build negative test reproducing a bug-851-class divergence. Boundary: owns src/lib/raft/raft_sim.c + harness/test files ONLY; does NOT modify the protocol implementation (raft.c/raft.h protocol semantics) — it consumes the raft-log-replication + raft-commit-safety entry points/callbacks verbatim. Depends: raft-log-replication, raft-commit-safety."
+}