Canonicalize plan/task orchestration model

  - Add durable project -> plan -> task shape with required plan membership
  - Replace task agents/owners with a single task session record
  - Make project descriptions required and hide admin project tools unless enabled
  - Add automatic task session replacement and stop old tmux sessions
  - Update CLI project creation, pruning, MCP schemas, docs, prompts, and skills
  - Migrate live store shape and sync installed mmux skills
  - Cover canonical model, session replacement, admin tooling, CLI, and store behavior with tests

Make coder profiles built-in and configurable

Move coder profile behavior into built-in Rust adapters and remove TOML/runtime profile loading.
Add enabled/default coder profile flags, including defaulting to the first enabled built-in unless overridden.
Update MCP schemas, tests, README, AGENTS, and Codex/Claude skills for the new profile model.

Project-id moved to UUID + id and slug accepted in toolcalls: both mu…

…st be globally unique.