fix: isolate concurrent OpenCode chat runs

tests/unit/opencode-session-run-machine.test.ts

@@ -33,11 +33,26 @@ describe('opencode session run machine', () => {
     });
     expect(isSessionRunActive(posting)).toBe(true);
 
-    const running = transitionSessionRunState(posting, {
+    const accepted = transitionSessionRunState(posting, {
       type: 'post_accepted',
       runId: 1,
     });
 
+    expect(accepted.phase).toBe('posting');
+    expect(isSessionRunActive(accepted)).toBe(true);
+
+    const earlyIdle = transitionSessionRunState(accepted, {
+      type: 'remote_idle',
+      runId: 1,
+    });
+
+    expect(earlyIdle).toEqual(accepted);
+
+    const running = transitionSessionRunState(earlyIdle, {
+      type: 'remote_busy',
+      runId: 1,
+    });
+
     expect(running.phase).toBe('running');
     expect(isSessionRunActive(running)).toBe(true);
   });
@@ -47,7 +62,11 @@ describe('opencode session run machine', () => {
       createIdleSessionRunState<TestPrompt>(),
       { type: 'send_started', runId: 2, promptId: 'msg_active' },
     );
-    const withQueue = transitionSessionRunState(running, {
+    const acknowledged = transitionSessionRunState(running, {
+      type: 'remote_busy',
+      runId: 2,
+    });
+    const withQueue = transitionSessionRunState(acknowledged, {
       type: 'queue_prompt',
       prompt: { id: 'queued_1', text: 'second' },
     });
@@ -173,7 +192,11 @@ describe('opencode session run machine', () => {
       createIdleSessionRunState<TestPrompt>(),
       { type: 'send_started', runId: 9, promptId: 'compact-ses_1' },
     );
-    const completed = transitionSessionRunState(posting, {
+    const running = transitionSessionRunState(posting, {
+      type: 'remote_busy',
+      runId: 9,
+    });
+    const completed = transitionSessionRunState(running, {
       type: 'remote_idle',
       runId: 9,
     });
@@ -195,7 +218,7 @@ describe('opencode session run machine', () => {
       { type: 'remote_failed' as const, runId: 10, error: 'POST failed after early idle' },
       {
         phase: 'idle',
-        queue: [{ id: 'queued_1', text: 'second' }],
+        queue: [],
         terminalReason: 'failed',
         error: 'POST failed after early idle',
       },