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/brainstorm/synthesis.md

@@ -48,7 +48,7 @@ Three-phase workflow to eliminate ambiguities and enhance conceptual depth in ro
 
 ### Phase 1: Discovery & Validation
 
-1. **Detect Session**: Use `--session` parameter or `.workflow/.active-*` marker
+1. **Detect Session**: Use `--session` parameter or find `.workflow/sessions/WFS-*` directories
 2. **Validate Files**:
    - `guidance-specification.md` (optional, warn if missing)
    - `*/analysis*.md` (required, error if empty)
@@ -59,7 +59,7 @@ Three-phase workflow to eliminate ambiguities and enhance conceptual depth in ro
 **Main flow prepares file paths for Agent**:
 
 1. **Discover Analysis Files**:
-   - Glob(.workflow/WFS-{session}/.brainstorming/*/analysis*.md)
+   - Glob(.workflow/sessions/WFS-{session}/.brainstorming/*/analysis*.md)
    - Supports: analysis.md, analysis-1.md, analysis-2.md, analysis-3.md
    - Validate: At least one file exists (error if empty)
 
@@ -69,7 +69,7 @@ Three-phase workflow to eliminate ambiguities and enhance conceptual depth in ro
 
 3. **Pass to Agent** (Phase 3):
    - `session_id`
-   - `brainstorm_dir`: .workflow/WFS-{session}/.brainstorming/
+   - `brainstorm_dir`: .workflow/sessions/WFS-{session}/.brainstorming/
    - `role_analysis_paths`: ["product-manager/analysis.md", "system-architect/analysis-1.md", ...]
    - `participating_roles`: ["product-manager", "system-architect", ...]
 
@@ -361,7 +361,7 @@ Updated {role2}/analysis.md with Clarifications section + enhanced content
 
 ## Output
 
-**Location**: `.workflow/WFS-{session}/.brainstorming/[role]/analysis*.md` (in-place updates)
+**Location**: `.workflow/sessions/WFS-{session}/.brainstorming/[role]/analysis*.md` (in-place updates)
 
 **Updated Structure**:
 ```markdown