fix: Prevent lost task completions after server restart

Three bugs causing empty phase diffs when server restarts during agent
execution:

1. Startup ordering race: reconcileAfterRestart() emitted agent:stopped
   before orchestrator registered listeners — events lost. Moved
   reconciliation to after orchestrator.start().

2. Stuck in_progress tasks: recoverDispatchQueues() only re-queued
   pending tasks. Added recovery for in_progress tasks whose agents
   are dead (not running/waiting_for_input).

3. Branch force-reset destroys work: git branch -f wiped commits when
   a second agent was dispatched for the same task. Now checks if the
   branch has commits beyond baseBranch before resetting.

Also adds:
- agent:crashed handler with auto-retry (MAX_TASK_RETRIES=3)
- retryCount column on tasks table + migration
- retryCount reset on manual retryBlockedTask()

apps/server/db/schema.ts

@@ -157,6 +157,7 @@ export const tasks = sqliteTable('tasks', {
     .default('pending'),
   order: integer('order').notNull().default(0),
   summary: text('summary'), // Agent result summary — propagated to dependent tasks as context
+  retryCount: integer('retry_count').notNull().default(0),
   createdAt: integer('created_at', { mode: 'timestamp' }).notNull(),
   updatedAt: integer('updated_at', { mode: 'timestamp' }).notNull(),
 });