feat(workflow): add project-level state management with intelligent initialization

Implement comprehensive project.json system for tracking project state, completed features, and architecture overview.

## New Features

### 1. /workflow:init Command (NEW)
- Independent project initialization command using cli-explore-agent
- Deep Scan mode analyzes: technology stack, architecture, key components, metrics
- Generates project.json with comprehensive overview field
- Supports --regenerate flag to update analysis while preserving features
- One-time initialization with intelligent project cognition

### 2. Enhanced session:start
- Added Step 0: Check project.json existence before session creation
- Auto-calls /workflow:init if project.json missing
- Separated project-level vs session-level initialization responsibilities

### 3. Enhanced session:complete
- Added Phase 3: Update Project Feature Registry
- Extracts feature metadata from IMPL_PLAN.md
- Records completed sessions as features in project.json
- Includes: title, description, tags, timeline, traceability (archive_path, commit_hash)
- Auto-generates feature IDs and tags from implementation plans

### 4. Enhanced status Command
- Added --project flag for project overview mode
- Displays: technology stack, architecture patterns, key components, metrics
- Shows completed features with full traceability
- Provides query commands for feature exploration

### 5. Enhanced context-gather
- Integrated project.json reading in context-search-agent workflow
- Phase 1: Load project.json overview as foundational context
- Phase 3: Populate context-package.json from project.json
- Prioritizes project.json context for architecture and tech stack
- Avoids redundant project analysis on every planning session

## Data Flow
project.json (init) → context-gather → context-package.json → task-generation
session-complete → project.json (features registry)

## Benefits
- Single source of truth for project state
- Efficient context reuse across sessions
- Complete feature traceability and history
- Consistent architectural baseline for all workflows

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

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

.claude/commands/workflow/session/start.md

@@ -13,6 +13,35 @@ examples:
 ## Overview
 Manages workflow sessions with three operation modes: discovery (manual), auto (intelligent), and force-new.
 
+**Dual Responsibility**:
+1. **Project-level initialization** (first-time only): Creates `.workflow/project.json` for feature registry
+2. **Session-level initialization** (always): Creates session directory structure
+
+## Step 0: Initialize Project State (First-time Only)
+
+**Executed before all modes** - Ensures project-level state file exists by calling `/workflow:init`.
+
+### Check and Initialize
+```bash
+# Check if project state exists
+bash(test -f .workflow/project.json && echo "EXISTS" || echo "NOT_FOUND")
+```
+
+**If NOT_FOUND**, delegate to `/workflow:init`:
+```javascript
+// Call workflow:init for intelligent project analysis
+SlashCommand({command: "/workflow:init"});
+
+// Wait for init completion
+// project.json will be created with comprehensive project overview
+```
+
+**Output**:
+- If EXISTS: `PROJECT_STATE: initialized`
+- If NOT_FOUND: Calls `/workflow:init` → creates `.workflow/project.json` with full project analysis
+
+**Note**: `/workflow:init` uses cli-explore-agent to build comprehensive project understanding (technology stack, architecture, key components). This step runs once per project. Subsequent executions skip initialization.
+
 ## Mode 1: Discovery Mode (Default)
 
 ### Usage