Split server.py into per-domain handler modules

[hrco]

Found in: pre-shipment review 2026-06-30
Parent: #7
File: xbridge_mcp/server.py (~1961 lines)

Violates project convention of small focused functions. Hard to navigate and maintain. Split into:

• chat.py — handle_grok_chat
• search.py — handle_grok_web_search, handle_grok_x_search
• sessions.py — session CRUD handlers
• chains.py — chain execution handlers
• images.py — image/video handlers
• docs.py — docs proxy handlers

[hrco]

@claude issues from pre-shipment review — please triage and assign.