teams: ephemeral lifecycle for Scheduled + Triggered planner modes

Migration 0033: adds teams.lifecycle ('permanent' | 'ephemeral') and a
topology_runs.team_id back-ref with a partial index for the sibling-in-
flight check.

cm-db repo:
- teams::insert_team_with_lifecycle (insert_team keeps the permanent default)
- topology_runs::enqueue_run_for_team (populates team_id)
- topology_runs::check_ephemeral_teardown — atomic SELECT that only
  returns Some when the team is ephemeral AND no siblings are still
  queued/running; carries the workspace + bound claw ids for cleanup.

cm-api:
- topology_worker post-terminal hook maybe_teardown_ephemeral_team
  runs deprovision_claw on each bound claw (best-effort; failures log
  but don't block Postgres deletion), then hard_purge each agent row,
  then delete_team.
- routes::teams::build_team_with_lifecycle (build_team keeps default);
  run_team enqueues with team_id.
- planner ScaffoldRequest gains mode; lifecycle_for(mode) sets the team
  to ephemeral for scheduled + triggered, permanent otherwise.

Frontend MasterPlannerModal passes mode in the scaffold payload so the
backend can derive lifecycle without duplicating the mode taxonomy.

Tests: 3 new (returns claws when no siblings, holds when siblings queued,
ignores permanent teams). 10/10 topology_jobs green; workspace clippy
--tests clean.

crates/cm-db/src/repo/teams.rs

@@ -37,6 +37,8 @@ pub struct TeamMember {
 }
 
 /// Insert a team (the topology graph). Members are added separately.
+/// Lifecycle defaults to `permanent`; use `insert_ephemeral_team` for the
+/// scheduled / triggered flows.
 pub async fn insert_team(
     pool: &PgPool,
     id: Uuid,
@@ -44,15 +46,31 @@ pub async fn insert_team(
     name: &str,
     kind: &str,
     graph: &Value,
+) -> Result<(), DbError> {
+    insert_team_with_lifecycle(pool, id, workspace_id, name, kind, graph, "permanent").await
+}
+
+/// Insert a team with an explicit `lifecycle` (`permanent` | `ephemeral`).
+/// Ephemeral teams are torn down after the last in-flight run terminates —
+/// see cm-api::topology_worker::maybe_teardown_ephemeral_team.
+pub async fn insert_team_with_lifecycle(
+    pool: &PgPool,
+    id: Uuid,
+    workspace_id: WorkspaceId,
+    name: &str,
+    kind: &str,
+    graph: &Value,
+    lifecycle: &str,
 ) -> Result<(), DbError> {
     sqlx::query!(
-        "INSERT INTO teams (id, workspace_id, name, kind, graph)
-         VALUES ($1, $2, $3, $4, $5)",
+        "INSERT INTO teams (id, workspace_id, name, kind, graph, lifecycle)
+         VALUES ($1, $2, $3, $4, $5, $6)",
         id,
         workspace_id.as_uuid(),
         name,
         kind,
         graph,
+        lifecycle,
     )
     .execute(pool)
     .await?;