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.

frontend/src/components/dashboard/ResearchCanvas.tsx

@@ -237,27 +237,82 @@ export function ResearchCanvas({
           )}
         </div>
 
-        {/* Description */}
-        <div style={{ display: "flex", flexDirection: "column", gap: 10 }}>
-          <div style={sectionHeader}>Description</div>
-          <pre
-            style={{
-              padding: 16,
-              borderRadius: 10,
-              background: "#101014",
-              border: "1px solid rgba(255,255,255,.06)",
-              color: "#eaeaee",
-              fontFamily: mono,
-              fontSize: 12.5,
-              lineHeight: 1.6,
-              whiteSpace: "pre-wrap",
-              wordBreak: "break-word",
-              margin: 0,
-            }}
-          >
-            {topic.description}
-          </pre>
-        </div>
+        {/* Draft (post-run) or Description (pre-run). Once the pipeline has
+            produced an outcome, reviewers should see that instead of the
+            prompt they started from. The prompt is still shown as a
+            collapsed reference below. */}
+        {topic.latest_outcome ? (
+          <>
+            <div style={{ display: "flex", flexDirection: "column", gap: 10 }}>
+              <div style={{ display: "flex", alignItems: "center", justifyContent: "space-between" }}>
+                <div style={sectionHeader}>Draft · v{topic.latest_outcome.version}</div>
+                <div style={{ fontFamily: mono, fontSize: 10, color: "#6a6a72" }}>
+                  produced {new Date(topic.latest_outcome.created_at).toLocaleString()}
+                </div>
+              </div>
+              <pre
+                style={{
+                  padding: 16,
+                  borderRadius: 10,
+                  background: "#0d0d10",
+                  border: "1px solid rgba(201,138,240,.2)",
+                  color: "#eaeaee",
+                  fontFamily: mono,
+                  fontSize: 12.5,
+                  lineHeight: 1.6,
+                  whiteSpace: "pre-wrap",
+                  wordBreak: "break-word",
+                  margin: 0,
+                  maxHeight: "62vh",
+                  overflow: "auto",
+                }}
+              >
+                {topic.latest_outcome.body_md}
+              </pre>
+            </div>
+            <details>
+              <summary style={{ ...sectionHeader, cursor: "pointer" }}>Original prompt</summary>
+              <pre
+                style={{
+                  padding: 14,
+                  marginTop: 8,
+                  borderRadius: 10,
+                  background: "#0a0a0c",
+                  border: "1px solid rgba(255,255,255,.05)",
+                  color: "#8a8a92",
+                  fontFamily: mono,
+                  fontSize: 11.5,
+                  lineHeight: 1.55,
+                  whiteSpace: "pre-wrap",
+                  wordBreak: "break-word",
+                }}
+              >
+                {topic.description}
+              </pre>
+            </details>
+          </>
+        ) : (
+          <div style={{ display: "flex", flexDirection: "column", gap: 10 }}>
+            <div style={sectionHeader}>Description</div>
+            <pre
+              style={{
+                padding: 16,
+                borderRadius: 10,
+                background: "#101014",
+                border: "1px solid rgba(255,255,255,.06)",
+                color: "#eaeaee",
+                fontFamily: mono,
+                fontSize: 12.5,
+                lineHeight: 1.6,
+                whiteSpace: "pre-wrap",
+                wordBreak: "break-word",
+                margin: 0,
+              }}
+            >
+              {topic.description}
+            </pre>
+          </div>
+        )}
 
         {/* Stage explainer + primary action */}
         <div style={{ display: "flex", flexDirection: "column", gap: 8 }}>