docs: promote raft-apply-decoupling spec family from /kiro-discovery

Adds the Raft Apply-Ordering & Hook Decoupling roadmap phase: canonical
pre-hooks -> raft commit -> apply -> notify ordering, with the raft protocol
step lifted out of the notification hook fan-out (root of the bug-795/828/
851/1060 divergence family). Decision: apply-after-commit via a single
shared apply_committed_entry() seam reused by online apply and restart
replay.

- raft-drive-async: full spec docs (brief/requirements/research/design)
  committed alongside its already-tracked tasks.md; async-drive prerequisite
  for the apply-decoupling work, sequenced to start first (threatens
  failover liveness today).
- raft-apply-decoupling: new spec (brief + facts-in-raft.md) covering the
  apply seam and the facts (WAL_MODE_RETAIN) apply-timing question (open
  decision D1).
- job-array-single-wal-record: promoted from backlog to a tracked spec,
  sequenced after raft-apply-decoupling.
- ha-consistency-invariants: add criterion 2.9 (Facts-Apply invariant),
  documenting the current on-receipt fact-reaction deviation this family
  will reconcile.
- raft-commit-safety / raft-log-replication: reconcile spec.json phase to
  "implemented" (both were mislabeled tasks-generated despite full 18/18
  and 24/24 task completion + raft_sim GO).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SDWVNQLKxqTVHh42cH7rV3

.kiro/specs/raft-drive-async/spec.json

@@ -0,0 +1,22 @@
+{
+  "feature_name": "raft-drive-async",
+  "created_at": "2026-06-25T11:37:13Z",
+  "updated_at": "2026-06-26T04:43:19Z",
+  "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
+}