fix: use zero initial progress for XState phase transitions to prevent regression

Setting phaseProgress and overallProgress to 0 (instead of 50) when
XState emits a phase-change event ensures the progress bar only moves
forward. Previously, XState would set progress to 50%, then the agent
would send its actual progress (e.g. 10%), causing the bar to visually
regress from 50% → 10%.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/frontend/src/main/task-state-manager.ts

@@ -362,17 +362,22 @@ export class TaskStateManager {
 
     const phase = XSTATE_TO_PHASE[xstateState] || 'idle';
 
-    // Emit execution progress with the phase derived from XState
+    // Emit execution progress with the phase derived from XState.
+    // IMPORTANT: Do NOT use Date.now() as sequenceNumber here — doing so would
+    // permanently block all subsequent agent execution-progress events, because
+    // the agent uses small sequential integers (1, 2, 3…) that are always less
+    // than a timestamp. Instead emit with sequenceNumber=0 so the agent's own
+    // events can continue updating phaseProgress once the phase is established.
     safeSendToRenderer(
       this.getMainWindow,
       IPC_CHANNELS.TASK_EXECUTION_PROGRESS,
       taskId,
       {
         phase,
-        phaseProgress: phase === 'complete' ? 100 : 50,
-        overallProgress: phase === 'complete' ? 100 : 50,
+        phaseProgress: phase === 'complete' ? 100 : 0,
+        overallProgress: phase === 'complete' ? 100 : 0,
         message: `State: ${xstateState}`,
-        sequenceNumber: Date.now()  // Use timestamp as sequence to ensure it's newer
+        sequenceNumber: 0
       },
       projectId
     );