standard: MCP settings template = boj-server cartridge config (WS6)

[hyperpolymath]

Goal

Define the canonical 'MCP settings template' as a boj-server cartridge config standard each repo can carry.

Do

• Define the cartridge/config schema from boj-server/cartridges + config; specify the per-repo artifact.
• Reuse boj-server's cartridge-proposal flow (don't reinvent). Rollout via the reposystem automation.

Context

Plan WS6. Resolved at planning: MCP template = boj cartridge config (owner).