feat: AI-suggested conventional title when PR title validation fails

[myakove]

Description

When a PR title fails conventional-title validation, use an AI CLI tool to suggest a proper title. The suggestion is included in the check run failure output.

Controlled by a new ai-features config section (global or per-repo).

Configuration

ai-features:
  ai-provider: "claude"    # claude | gemini | cursor
  ai-model: "claude-opus-4-6[1m]"

Behavior

• When conventional-title check fails AND ai-features is configured:
  • Call the AI CLI with the PR title, diff context, and allowed types
  • Include the AI-suggested title in the check run failure output
• On any error (CLI failure, timeout, etc.): log the error, continue without suggestion
• Never break the PR flow

Deliverables

• Create webhook_server/libs/ai_cli.py - shared AI CLI wrapper (call_ai_cli function)
• Add ai-features config schema (global + per-repo)
• Integrate AI suggestion into conventional-title check run failure output
• Add tests
• Update example configs, README, CLAUDE.md