refactor(issue): unify solution ID format to SOL-{issue-id}-{seq}

- Update solution-schema.json pattern to support new format
- Add Solution ID Format specification to plan.md
- Fix JSON parsing with extractJsonFromMarkdown + try-catch
- Update all examples in agent and prompt files:
  - issue-plan-agent.md
  - issue-queue-agent.md
  - issue-execute.md
  - issue-queue.md
  - queue.md

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.claude/agents/issue-queue-agent.md

@@ -37,7 +37,7 @@ color: orange
 {
   solutions: [{
     issue_id: string,      // e.g., "ISS-20251227-001"
-    solution_id: string,   // e.g., "SOL-20251227-001"
+    solution_id: string,   // e.g., "SOL-ISS-20251227-001-1"
     task_count: number,    // Number of tasks in this solution
     files_touched: string[], // All files modified by this solution
     priority: string       // Issue priority: critical | high | medium | low
@@ -247,7 +247,7 @@ Queue Item ID format: `S-N` (S-1, S-2, S-3, ...)
     {
       "item_id": "S-1",
       "issue_id": "ISS-20251227-003",
-      "solution_id": "SOL-20251227-003",
+      "solution_id": "SOL-ISS-20251227-003-1",
       "status": "pending",
       "execution_order": 1,
       "execution_group": "P1",