research pipeline v2: topology-aware start + persisted draft

Three connected changes that turn "Start research" from a status
flip into a real pipeline that produces a reviewable artifact:

- Migration 0036: adds research_topics.topology_kind (default
  'hub_spoke') and a new research_outcomes table
  (id, topic_id, version DESC, body_md, produced_by_run_id, created_at)
  so each run's final synthesis is versioned and persistent.

- Wizard now has a topology picker in the Outcome step —
  hub_spoke / pipeline / hierarchical / star_moe — with copy that
  steers users to the right shape (Pipeline for research → distill
  → analyze → implement rosters, hub_spoke for the coordinator-
  and-specialists default).

- start_topic reads the chosen topology_kind, parses it into a
  cm_topology::TopologyKind, and dispatches a per-shape coordinator
  prompt via build_coordinator_task. Pipeline explicitly tells
  stage 1 not to write the final artifact and propagates a
  "final stage MUST emit a complete markdown document with
  measurable acceptance criteria" instruction downstream. The
  graph builder is called with the topology the user actually
  picked instead of hard-coded HubSpoke.

- topology_worker::freeze_research_outcome fires after every
  successful complete(). It looks up research_topic_id on the run;
  if set and final_output is non-empty, it inserts a new
  research_outcomes row (version auto-derived server-side via
  coalesce(max(version), 0) + 1). Best-effort — a DB hiccup logs
  but doesn't fail the run.

- TopicDetail now includes topology_kind and latest_outcome.
  ResearchCanvas swaps in the outcome's body_md (rendered as
  pre-wrap markdown, versioned header, produced-at timestamp)
  whenever an outcome exists; the original prompt collapses into
  an "Original prompt" <details> below so it's still one click
  away. Pre-run topics still show the description as before.

Follow-ups still open: reject-with-revision loop feeding the
coordinator, publishing → published transition + real artifact
export (md / pdf), and an approvals inbox surface for reviewers.

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

@@ -24,6 +24,9 @@ pub struct ResearchTopic {
     pub created_at: OffsetDateTime,
     pub updated_at: OffsetDateTime,
     pub published_at: Option<OffsetDateTime>,
+    /// Topology shape start_topic builds when firing this topic. Options:
+    /// hub_spoke, pipeline, hierarchical, star_moe. Defaults to hub_spoke.
+    pub topology_kind: String,
 }
 
 #[derive(Debug, Clone, Serialize)]
@@ -39,18 +42,20 @@ pub async fn create(
     title: &str,
     description: &str,
     outcome_kind: &str,
+    topology_kind: &str,
     created_by: Uuid,
 ) -> Result<Uuid, DbError> {
     let id = Uuid::now_v7();
     sqlx::query!(
         "INSERT INTO research_topics
-            (id, workspace_id, title, description, outcome_kind, status, created_by)
-         VALUES ($1, $2, $3, $4, $5, 'standby', $6)",
+            (id, workspace_id, title, description, outcome_kind, topology_kind, status, created_by)
+         VALUES ($1, $2, $3, $4, $5, $6, 'standby', $7)",
         id,
         workspace_id,
         title,
         description,
         outcome_kind,
+        topology_kind,
         created_by,
     )
     .execute(pool)
@@ -63,7 +68,7 @@ pub async fn list(pool: &PgPool, workspace_id: Uuid) -> Result<Vec<ResearchTopic
     let rows = sqlx::query_as!(
         ResearchTopic,
         "SELECT id, workspace_id, title, description, outcome_kind, status,
-                created_by, created_at, updated_at, published_at
+                created_by, created_at, updated_at, published_at, topology_kind
            FROM research_topics
           WHERE workspace_id = $1
           ORDER BY updated_at DESC",
@@ -82,7 +87,7 @@ pub async fn get(
     let row = sqlx::query_as!(
         ResearchTopic,
         "SELECT id, workspace_id, title, description, outcome_kind, status,
-                created_by, created_at, updated_at, published_at
+                created_by, created_at, updated_at, published_at, topology_kind
            FROM research_topics
           WHERE id = $1 AND workspace_id = $2",
         id,