feat(repos): add an "Initialize mise" option to the add-repo step

Some repos an operator wants to manage don't yet define the `.mise.toml`
`[tasks.test]` task the spawn gate hard-requires — a chicken-and-egg,
since you can't run an agent to author that file without it. This adds a
one-click bootstrap.

Ticking "Initialize mise" on the add step enqueues a `mise_init` command
after the clone. The worker launches a dedicated agent that detects the
repo's stack, writes a `.mise.toml` with a canonical `[tasks.test]` task,
and commits + pushes it. That agent runs with the test-task gate off
(creating the task is the point) and a `HANDLER_MISE_INIT` marker on, so
its hooks enforce a bootstrap contract instead of the normal test gate:

- Stop hook blocks the turn until `.mise.toml` defines `[tasks.test]` and
  the change is committed (clean tree) and pushed (no commits ahead of an
  upstream) — so claude cannot end before the work has actually landed.
- git-push hook lets the bootstrap push through, skipping the test/build
  gate (there may be no working suite yet) so the file reaches the remote.

Backend: `mise_init` command type (+ migration 0006), a shared
`control.mise` helper for the test-task check, `spawn(require_tests=,
mise_init=)`, gitops `is_clean`/`ahead_count`, and `init_mise` on the
project-create API (only acts when a git remote exists to push to).
Frontend: the checkbox, plumbed through the store, following the launch.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BxKY28XKCM6o4ag3nmaVsZ

frontend/lib/api.ts

@@ -18,6 +18,9 @@ export interface Project {
   created_at: string;
   /* Present on the registration response in git-server mode: the enqueued clone. */
   sync_command_id?: number | null;
+  /* Present on the registration response when "Initialize mise" was ticked: the
+   * enqueued bootstrap agent that writes + commits + pushes a .mise.toml. */
+  mise_init_command_id?: number | null;
 }
 
 export interface Agent {