fix: enable dashboard reply scheduler wakeups

[numnx]

What changed

• Removed task scheduling from the restricted scheduler_code_ux surface so assigned agents can only create their own wakeups.
• Enabled full built-in Code UX MCP access plus scheduler_code_ux by default for assigned dashboard reply agents.
• Added wakeAfterReply so a dashboard reply agent can answer first, then immediately wake and continue with MCP work after the reply is sent.
• Added sprint/task completion wakeup anchors for agent-owned follow-ups, including task-end evidence resolution.
• Updated Project manager instructions and docs for sprint-planning delegation and scheduler usage.

Why

Project manager dashboard replies need to coordinate longer Code UX workflows without blocking the first response or inventing implementation task lists manually. The restricted scheduler should support only self-wakeups while still allowing immediate continuations and completion-triggered reports.

Validation

• pnpm exec vitest run tests/backend/mcp/management-scheduler-actions.test.ts tests/backend/mcp/tool-validators.test.ts tests/backend/services/scheduler-service.test.ts tests/backend/services/chat-thread-runtime-service.test.ts tests/backend/services/agent-mcp-access.test.ts tests/backend/services/worker-inbox-reply-service.test.ts tests/backend/services/chat-reply-prompt.test.ts
• pnpm run lint
• pnpm run build
• pnpm run test:backend

Risk / rollback

Risk is concentrated in dashboard reply MCP access and scheduler wakeup dispatch. Roll back this commit to restore the prior scheduler contract and dashboard reply access behavior.