feat(grok): deliver Auto Title skill and process-local hook guidance #1215

Problem

Grok panes can receive Auto Title's built-in MCP tool, but Agent Code cannot currently deliver the managed Auto Title skill to Grok. registry.main.ts declares Grok personal skills unsupported because native skill discovery has not been recorded; targets.ts skips Grok during product-skill materialization. Grok also has no app-injected turn reminder through the current grok-code-headless adapter.

Current behavior

With Auto Title enabled, Grok receives title_set, its detailed tool description, and MCP server instructions. The product documentation for #1210 explicitly states the missing managed skill and hook coverage.

Desired outcome

Verify Grok's installed native skill-discovery and process-local Stop-hook contracts, then deliver managed guidance and a bounded missing-title reminder without editing machine-wide or project hook configuration. Record binary-backed provider tests before changing the support claim.