fix(workflow): complete path migration and enhance session:complete

Comprehensive update to eliminate all old path references and implement transactional archival in session:complete.

## Part 1: Complete Path Migration (43 files)

### Files Updated
- action-plan-verify.md
- session/list.md, session/resume.md
- tdd-verify.md, tdd-plan.md, test-*.md
- All brainstorm/*.md files (13 files)
- All tools/*.md files (10 files)
- All ui-design/*.md files (10 files)
- lite-plan.md, lite-execute.md, plan.md

### Path Changes
- `.workflow/.active-*` → `find .workflow/sessions/ -name "WFS-*" -type d`
- `.workflow/WFS-{session}` → `.workflow/sessions/WFS-{session}`
- `.workflow/.archives/` → `.workflow/archives/`
- Removed all marker file operations (touch/rm .active-*)

### Verification
- ✅ 0 references to .active-* markers remain
- ✅ 0 references to direct .workflow/WFS-* paths
- ✅ 0 references to .workflow/.archives/ (dot prefix)

## Part 2: Transactional Archival Enhancement

### session/complete.md - Complete Rewrite

**New Four-Phase Architecture**:

1. **Phase 1: Pre-Archival Preparation**
   - Find active session in .workflow/sessions/
   - Check for existing .archiving marker (resume detection)
   - Create .archiving marker to prevent concurrent operations

2. **Phase 2: Agent Analysis (In-Place)**
   - Agent processes session WHILE STILL in sessions/ directory
   - Pure analysis - no file moves or manifest updates
   - Returns complete metadata package for atomic commit
   - Failure here → session remains active, safe to retry

3. **Phase 3: Atomic Commit**
   - Only executes if Phase 2 succeeds
   - Move session to archives/
   - Update manifest.json
   - Remove .archiving marker
   - All-or-nothing guarantee

4. **Phase 4: Project Registry Update**
   - Extract feature metadata and update project.json

**Key Improvements**:
- **Agent-first, move-second**: Prevents inconsistent states
- **Transactional guarantees**: All-or-nothing file operations
- **Resume capability**: .archiving marker enables safe retry
- **Error recovery**: Comprehensive failure handling documented

**Old Design Flaw (Fixed)**:
- Old: Move first → Agent processes → If agent fails, session moved but metadata incomplete
- New: Agent processes → If success, atomic commit → Guaranteed consistency

## Benefits

1. **Consistency**: All commands use identical path patterns
2. **Robustness**: Transactional archival prevents data loss
3. **Maintainability**: Single source of truth for directory structure
4. **Recoverability**: Failed operations can be safely retried
5. **Alignment**: Closer to OpenSpec's clean three-layer model

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

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

.claude/commands/workflow/tools/task-generate.md

@@ -224,7 +224,7 @@ Each task JSON embeds all necessary context, artifacts, and execution steps usin
 - `id`: Task identifier (format: `IMPL-N` or `IMPL-N.M` for subtasks)
 - `title`: Descriptive task name
 - `status`: Task state (`pending|active|completed|blocked|container`)
-- `context_package_path`: Path to context package (`.workflow/WFS-[session]/.process/context-package.json`)
+- `context_package_path`: Path to context package (`.workflow/sessions/WFS-[session]/.process/context-package.json`)
 - `meta`: Task metadata
 - `context`: Task-specific context and requirements
 - `flow_control`: Execution steps and workflow
@@ -269,7 +269,7 @@ Each task JSON embeds all necessary context, artifacts, and execution steps usin
   "id": "IMPL-1",
   "title": "Implement feature X with Y components",
   "status": "pending",
-  "context_package_path": ".workflow/WFS-session/.process/context-package.json",
+  "context_package_path": ".workflow/sessions/WFS-session/.process/context-package.json",
   "meta": {
     "type": "feature",
     "agent": "@code-developer",
@@ -291,7 +291,7 @@ Each task JSON embeds all necessary context, artifacts, and execution steps usin
     "depends_on": [],
     "artifacts": [
       {
-        "path": ".workflow/WFS-session/.brainstorming/system-architect/analysis.md",
+        "path": ".workflow/sessions/WFS-session/.brainstorming/system-architect/analysis.md",
         "priority": "highest",
         "usage": "Architecture decisions and API specifications"
       }