docs(kiro): reconcile spec metadata, promote 3 new specs, fix template path

- config-upgrade-snapshot, raft-adapter-conformance: correct stale
  phase metadata (both showed "tasks-generated" though every task was
  already complete) and record their validate-impl GO decisions with
  known-limitations notes (bug-1471/bug-1472-remainder, bug-1474
  angle-b) for future spec ownership.
- component-failover-adoption: catch up design/requirements/research
  docs to the Phase 6 fix (bug-1548/bug-1549, commit d479b707) that
  landed after this spec was already marked closed.
- Promote 3 roadmap backlog items to specs (2026-08-10 discovery):
  component-rejoin-resync (apiserver/scheduler rejoin resync),
  worker-rejoin-resync (worker job-fact resync, hard prereq for
  raft-apply-decoupling's facts half), scheduler-sim-diagnostics
  (open-ended scheduler REPL debug/troubleshoot capability).
- roadmap.md updated to reflect all of the above.
- kiro-steering/kiro-steering-custom SKILL.md: fix stale template path
  (templates/steering/ -> .kiro/settings/templates/steering/) plus
  minor doc corrections in the other kiro-spec-* skills.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

.claude/skills/kiro-spec-quick/SKILL.md

@@ -72,10 +72,10 @@ Execute these 4 phases in order:
 
 5. **Initialize Files from Templates**:
 
-   a. Read templates from this skill's directory:
+   a. Read templates:
    ```
-   - templates/specs/init.json
-   - templates/specs/requirements-init.md
+   - .kiro/settings/templates/specs/init.json
+   - .kiro/settings/templates/specs/requirements-init.md
    ```
 
    b. Replace placeholders:
@@ -230,7 +230,7 @@ Next Steps:
 ### Error Scenarios
 
 **Template Missing**:
-- Check `templates/specs/` in this skill's directory exists
+- Check `.kiro/settings/templates/specs/` exists
 - Report specific missing file
 - Exit with error