Add managed project router state

[hmishra2250]

Summary

• add the exact frozen project-local router card and skill-description prefix
• manage project router state with provenance-bound skill selection, transactional writes, opt-out, drift detection, and precise removal
• preserve user content and refuse unsafe or malformed state rather than overclaiming configuration

Scope

This is the state/lifecycle foundation only. It does not activate default delivery by itself. Launch integration is stacked separately in #157, and the default-on release decision remains gated by the fresh P1 experiment.

Frozen treatment

• card SHA-256: df867193a6fe011342fce14b770e497cf667ca755e396bb16bbb52c513627951
• skill-prefix SHA-256: 4d01a7080b1493975b0ea07a95db17c5a4f3b9030c0f5f237da9e634559c0cbd
• project scope only; no global instruction-file writes

Review

• stacked on Secure hosted MCP credential setup #155
• one semantic commit, preserved; do not squash
• the full candidate stack passed 418/418 tests, typecheck, build, formatting, diff checks, and independent review