fix(cli): include __start__ message in nerve thread show

When 'nerve thread show' is called without --before, the initial user
prompt (__start__ message) is now displayed first, followed by the most
recent role rounds within the budget.

- Add getThreadStartMessage() to LogStore
- Modify buildThreadCommandOutput to accept optional startRow
- Pass start message from threadShowCommand when before===0
- Add tests for new behavior

Fixes #231

packages/store/src/__tests__/log-store-crash-recovery.test.ts

@@ -255,5 +255,51 @@ describe("LogStore — crash recovery helpers (Phase 3)", () => {
       expect(store.getThreadRoundCount("missing")).toBe(0);
       expect(store.getThreadRounds("missing", { before: 0, limit: 10 })).toHaveLength(0);
     });
+
+    it("getThreadStartMessage returns __start__ row with round 0 and excludes it from getThreadRounds", () => {
+      store.append({
+        source: "workflow",
+        type: "thread_workflow_message",
+        refId: "run-start",
+        payload: JSON.stringify({
+          role: "__start__",
+          content: "launch",
+          meta: { prompt: "hi" },
+          timestamp: 50,
+        }),
+        timestamp: 50,
+      });
+      store.append({
+        source: "workflow",
+        type: "thread_command_event",
+        refId: "run-start",
+        payload: JSON.stringify({ type: "step_a", role: "alpha", content: "hello", meta: {} }),
+        timestamp: 51,
+      });
+
+      expect(store.getThreadRoundCount("run-start")).toBe(1);
+
+      const start = store.getThreadStartMessage("run-start");
+      expect(start).not.toBeNull();
+      expect(start?.round).toBe(0);
+      expect(start?.message.role).toBe("__start__");
+      expect(start?.message.content).toBe("launch");
+
+      const rounds = store.getThreadRounds("run-start", { before: 0, limit: 50 });
+      expect(rounds).toHaveLength(1);
+      expect(rounds[0].round).toBe(1);
+      expect(rounds[0].message.role).toBe("alpha");
+    });
+
+    it("getThreadStartMessage returns null when no __start__ message", () => {
+      store.append({
+        source: "workflow",
+        type: "thread_command_event",
+        refId: "run-no-start",
+        payload: JSON.stringify({ type: "step_a", role: "alpha", content: "x", meta: {} }),
+        timestamp: 1,
+      });
+      expect(store.getThreadStartMessage("run-no-start")).toBeNull();
+    });
   });
 });

packages/store/src/log-store.ts

@@ -166,6 +166,11 @@ export type LogStore = {
    * with `round` from ROW_NUMBER() OVER (ORDER BY id ASC). No schema migration — numbering is computed in SQL.
    */
   getThreadRounds: (runId: string, params: GetThreadRoundsParams) => ThreadRoundRow[];
+  /**
+   * The workflow `__start__` message for a run (if persisted), as a {@link ThreadRoundRow}
+   * with `round` 0 — not part of {@link getThreadRoundCount} / {@link getThreadRounds} numbering.
+   */
+  getThreadStartMessage: (runId: string) => ThreadRoundRow | null;
   /**
    * Export logs older than the retention window to `data/archive/logs/YYYY-MM-DD.jsonl`,
    * then delete those rows and advance `meta.archived_up_to` in one transaction per day
@@ -396,6 +401,15 @@ export function createLogStore(dbPath: string): LogStore {
      LIMIT @lim`,
   );
 
+  const getThreadStartMessageStmt = sqlite.prepare(
+    `SELECT id, timestamp, payload FROM logs
+     WHERE source = 'workflow' AND type IN ('thread_command_event', 'thread_workflow_message') AND ref_id = ?
+       AND payload IS NOT NULL AND json_valid(payload) = 1
+       AND COALESCE(json_extract(payload, '$.role'), '') = '__start__'
+     ORDER BY id ASC
+     LIMIT 1`,
+  );
+
   const getActiveWorkflowRunsStmt = sqlite.prepare(
     "SELECT run_id, workflow, status, timestamp, exit_code FROM workflow_runs WHERE status IN ('queued', 'started') ORDER BY timestamp ASC",
   );
@@ -676,6 +690,16 @@ export function createLogStore(dbPath: string): LogStore {
     return out;
   }
 
+  function getThreadStartMessage(runId: string): ThreadRoundRow | null {
+    const row = getThreadStartMessageStmt.get(runId) as
+      | { id: number; timestamp: number; payload: string | null }
+      | undefined;
+    if (row === undefined || row.payload === null) return null;
+    const message = parseRoundPayload(row.payload, row.timestamp);
+    if (message === null) return null;
+    return { round: 0, logId: row.id, timestamp: row.timestamp, message };
+  }
+
   function archiveDayTx(day: string, start: number, endExclusive: number): void {
     runInTransaction(sqlite, () => {
       deleteLogsForDayStmt.run({ start, endExclusive });
@@ -743,6 +767,7 @@ export function createLogStore(dbPath: string): LogStore {
     getThreadMessages,
     getThreadRoundCount,
     getThreadRounds,
+    getThreadStartMessage,
     archiveLogs,
     close,
   };