[M5] CLI Chat Interface (docgen chat)

[cursor]

Milestone 5 — Embedded AI via Embabel | Priority: Medium | COMPLETED in PR #27

Terminal-based conversational interface for docgen pipeline control.

• Interactive chat loop with colored prompt
• /help, /status, /clear, /quit slash commands
• Project context injection (segments, files, visual_map)
• --non-interactive mode for scripted usage
• --provider and --model overrides

Implemented in src/docgen/chat.py. See issues/embedded-ai-embabel/14-cli-chat.md.