feat: implement enterprise workflow with multi-backend support

## Overview
Complete implementation of enterprise-level workflow features including
multi-backend execution (Codex/Claude/Gemini), GitHub issue-to-PR automation,
hooks system, and comprehensive documentation.

## Major Changes

### 1. Multi-Backend Support (codeagent-wrapper)
- Renamed codex-wrapper → codeagent-wrapper
- Backend interface with Codex/Claude/Gemini implementations
- Multi-format JSON stream parser (auto-detects backend)
- CLI flag: --backend codex|claude|gemini (default: codex)
- Test coverage: 89.2%

**Files:**
- codeagent-wrapper/backend.go - Backend interface
- codeagent-wrapper/parser.go - Multi-format parser
- codeagent-wrapper/config.go - CLI parsing with backend selection
- codeagent-wrapper/executor.go - Process execution
- codeagent-wrapper/logger.go - Async logging
- codeagent-wrapper/utils.go - Utilities

### 2. GitHub Workflow Commands
- /gh-create-issue - Create structured issues via guided dialogue
- /gh-implement - Issue-to-PR automation with full dev lifecycle

**Files:**
- github-workflow/commands/gh-create-issue.md
- github-workflow/commands/gh-implement.md
- skills/codeagent/SKILL.md

### 3. Hooks System
- UserPromptSubmit hook for skill activation
- Pre-commit example with code quality checks
- merge_json operation in install.py for settings.json merging

**Files:**
- hooks/skill-activation-prompt.sh|.js
- hooks/pre-commit.sh
- hooks/hooks-config.json
- hooks/test-skill-activation.sh

### 4. Skills System
- skill-rules.json for auto-activation
- codeagent skill for multi-backend wrapper

**Files:**
- skills/skill-rules.json
- skills/codeagent/SKILL.md
- skills/codex/SKILL.md (updated)

### 5. Installation System
- install.py: Added merge_json operation
- config.json: Added "gh" module
- config.schema.json: Added op_merge_json schema

### 6. CI/CD
- GitHub Actions workflow for testing and building

**Files:**
- .github/workflows/ci.yml

### 7. Comprehensive Documentation
- Architecture overview with ASCII diagrams
- Codeagent-wrapper complete usage guide
- GitHub workflow detailed examples
- Hooks customization guide

**Files:**
- docs/architecture.md (21KB)
- docs/CODEAGENT-WRAPPER.md (9KB)
- docs/GITHUB-WORKFLOW.md (9KB)
- docs/HOOKS.md (4KB)
- docs/enterprise-workflow-ideas.md
- README.md (updated with doc links)

## Test Results
- All tests passing ✅
- Coverage: 89.2%
- Security scan: 0 issues (gosec)

## Breaking Changes
- codex-wrapper renamed to codeagent-wrapper
- Default backend: codex (documented in README)

## Migration Guide
Users with codex-wrapper installed should:
1. Run: python3 install.py --module dev --force
2. Update shell aliases if any

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

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

skills/codeagent/SKILL.md

@@ -0,0 +1,101 @@
+---
+name: codeagent
+description: Execute codeagent-wrapper for multi-backend AI code tasks. Supports Codex, Claude, and Gemini backends with file references (@syntax) and structured output.
+---
+
+# Codeagent Wrapper Integration
+
+## Overview
+
+Execute codeagent-wrapper commands with pluggable AI backends (Codex, Claude, Gemini). Supports file references via `@` syntax and parallel task execution.
+
+## When to Use
+
+- Complex code analysis requiring deep understanding
+- Large-scale refactoring across multiple files
+- Automated code generation with backend selection
+
+## Usage
+
+**HEREDOC syntax** (recommended):
+```bash
+codeagent-wrapper - [working_dir] <<'EOF'
+<task content here>
+EOF
+```
+
+**With backend selection**:
+```bash
+codeagent-wrapper --backend claude - <<'EOF'
+<task content here>
+EOF
+```
+
+**Simple tasks**:
+```bash
+codeagent-wrapper "simple task" [working_dir]
+codeagent-wrapper --backend gemini "simple task"
+```
+
+## Backends
+
+| Backend | Command | Description |
+|---------|---------|-------------|
+| codex | `--backend codex` | OpenAI Codex (default) |
+| claude | `--backend claude` | Anthropic Claude |
+| gemini | `--backend gemini` | Google Gemini |
+
+## Parameters
+
+- `task` (required): Task description, supports `@file` references
+- `working_dir` (optional): Working directory (default: current)
+- `--backend` (optional): Select AI backend (codex/claude/gemini)
+
+## Return Format
+
+```
+Agent response text here...
+
+---
+SESSION_ID: 019a7247-ac9d-71f3-89e2-a823dbd8fd14
+```
+
+## Resume Session 
+
+```bash
+codeagent-wrapper resume <session_id> - <<'EOF'
+<follow-up task>
+EOF
+```
+
+## Parallel Execution
+
+```bash
+codeagent-wrapper --parallel <<'EOF'
+---TASK---
+id: task1
+workdir: /path/to/dir
+---CONTENT---
+task content
+---TASK---
+id: task2
+dependencies: task1
+---CONTENT---
+dependent task
+EOF
+```
+
+## Environment Variables
+
+- `CODEX_TIMEOUT`: Override timeout in milliseconds (default: 7200000)
+
+## Invocation Pattern
+
+```
+Bash tool parameters:
+- command: codeagent-wrapper --backend <backend> - [working_dir] <<'EOF'
+  <task content>
+  EOF
+- timeout: 7200000
+- description: <brief description>
+```