Keep stop_reason on collected wait_agents projections

The occupancy collector is the wait_agents JSON shape. Dropping
stopReason there made interrupt and incomplete-report waits look
clean after collection.

Author: TheGreatAxios

src/subagent/fleet-dry-drive.test.ts

@@ -217,6 +217,25 @@ describe("collectUncollectedTerminals", () => {
     expect(records.get("ghost")?.collected).toBe(true);
   });
 
+  test("projects mailbox stopReason as stop_reason", () => {
+    const records = new Map<string, FleetDryMailboxRecord>([
+      ["w1", { status: "interrupted", report: "salvage", stopReason: "interrupted" }],
+    ]);
+    const mailbox: FleetDryMailbox = {
+      ids: () => [...records.keys()],
+      peek: (id) => records.get(id),
+      take: (id) => records.get(id),
+    };
+    expect(collectUncollectedTerminals(mailbox, [], true)).toEqual([
+      {
+        agent_id: "w1",
+        status: "interrupted",
+        report: "salvage",
+        stop_reason: "interrupted",
+      },
+    ]);
+  });
+
   test("clips oversized reports", () => {
     const records = new Map<string, FleetDryMailboxRecord>([
       ["big", { status: "done", report: "x".repeat(FLEET_DRY_REPORT_CHARS + 40) }],

src/subagent/fleet-dry-drive.ts

@@ -20,6 +20,7 @@ export interface FleetDryMailboxRecord {
   readonly description?: string;
   readonly hint?: string;
   readonly providerFailure?: true;
+  readonly stopReason?: string;
 }
 
 export interface FleetDryMailbox {
@@ -43,6 +44,7 @@ export interface CollectedWorkerReport {
   error?: string;
   hint?: string;
   provider_failure?: true;
+  stop_reason?: string;
 }
 
 export function shouldDriveOpenTasks(input: {
@@ -85,6 +87,7 @@ export function projectMailboxRecord(
     ...(error !== undefined ? { error } : {}),
     ...(taken.hint !== undefined ? { hint: taken.hint } : {}),
     ...(taken.providerFailure === true ? { provider_failure: true } : {}),
+    ...(taken.stopReason !== undefined ? { stop_reason: taken.stopReason } : {}),
   };
 }