feat(KB-635): integrate mission workflows across CLI, extension, and engine

- Add mission CLI commands and pi extension tools for creating missions, milestones, slices, features, and task links
- Extend core mission storage and schema migrations with auto-advance support, task slice linkage, and comment normalization coverage
- Wire mission-aware scheduler and executor behavior so linked features progress with task execution and completed slices can auto-activate follow-on work
- Add regression tests for mission CLI parsing, extension behaviors, scheduler mission semantics, and executor integration

packages/engine/src/runtimes/in-process-runtime.ts

@@ -125,10 +125,12 @@ export class InProcessRuntime
       this.globalSemaphore = new AgentSemaphore(() => globalLimit);
 
       // 4. Initialize Scheduler
+      const missionStore = this.taskStore.getMissionStore();
       this.scheduler = new Scheduler(this.taskStore, {
         maxConcurrent: this.config.maxConcurrent,
         maxWorktrees: this.config.maxWorktrees,
         semaphore: this.globalSemaphore,
+        missionStore,
         onSchedule: (task) => {
           this.recordActivity();
           runtimeLog.log(`Scheduled task ${task.id}`);
@@ -144,6 +146,10 @@ export class InProcessRuntime
         pool: this.worktreePool,
         usageLimitPauser: this.usageLimitPauser,
         stuckTaskDetector: this.stuckTaskDetector,
+        missionStore,
+        onSliceComplete: (slice) => {
+          void this.scheduler.onSliceComplete(slice);
+        },
         onStart: (task, worktreePath) => {
           this.recordActivity();
           runtimeLog.log(`Started executing task ${task.id} in ${worktreePath}`);