Add subagents for discussion, document generation, and code exploration

- Introduced Discuss Subagent for lightweight multi-perspective critique, reducing overhead from ~60-90s to ~5s.
- Added Doc Generation Subagent for generating documents with CLI analysis and template filling.
- Implemented Explore Subagent for centralized codebase exploration with caching, replacing the standalone explorer role.
- Created templates for architecture documents, epics, product briefs, and requirements PRD to standardize outputs.
- Added a review file for tracking changes and discussions.

.claude/skills/team-lifecycle/role-specs/executor.md

@@ -0,0 +1,67 @@
+---
+role: executor
+prefix: IMPL
+inner_loop: true
+discuss_rounds: []
+subagents: []
+message_types:
+  success: impl_complete
+  progress: impl_progress
+  error: error
+---
+
+# Executor — Phase 2-4
+
+## Phase 2: Task & Plan Loading
+
+**Objective**: Load plan and determine execution strategy.
+
+1. Load plan.json and .task/TASK-*.json from `<session-folder>/plan/`
+
+**Backend selection** (priority order):
+
+| Priority | Source | Method |
+|----------|--------|--------|
+| 1 | Task metadata | task.metadata.executor field |
+| 2 | Plan default | "Execution Backend:" in plan |
+| 3 | Auto-select | Simple (< 200 chars, no refactor) → agent; Complex → codex |
+
+**Code review selection**:
+
+| Priority | Source | Method |
+|----------|--------|--------|
+| 1 | Task metadata | task.metadata.code_review field |
+| 2 | Plan default | "Code Review:" in plan |
+| 3 | Auto-select | Critical keywords (auth, security, payment) → enabled |
+
+## Phase 3: Code Implementation
+
+**Objective**: Execute implementation across batches.
+
+**Batching**: Topological sort by IMPL task dependencies → sequential batches.
+
+| Backend | Invocation | Use Case |
+|---------|-----------|----------|
+| agent | `Task({ subagent_type: "code-developer", run_in_background: false })` | Simple, direct edits |
+| codex | `ccw cli --tool codex --mode write` (background) | Complex, architecture |
+| gemini | `ccw cli --tool gemini --mode write` (background) | Analysis-heavy |
+
+## Phase 4: Self-Validation
+
+| Step | Method | Pass Criteria |
+|------|--------|--------------|
+| Syntax check | `tsc --noEmit` (30s) | Exit code 0 |
+| Acceptance criteria | Match criteria keywords vs implementation | All addressed |
+| Test detection | Find .test.ts/.spec.ts for modified files | Tests identified |
+| Code review (optional) | gemini analysis or codex review | No blocking issues |
+
+**Report**: task ID, status, files modified, validation results, backend used.
+
+## Error Handling
+
+| Scenario | Resolution |
+|----------|------------|
+| Syntax errors | Retry with error context (max 3) |
+| Missing dependencies | Request from coordinator |
+| Backend unavailable | Fallback to agent |
+| Circular dependencies | Abort, report graph |