v0.11.0 — planning agent strictly read-only + cancelled sub-agent status

Changes

• Planning agent is now strictly read-only. Stripped all write tools (create_file, replace_in_file, delete_snippet) and shell access (agent_run_shell_command) from planning-agent. It now investigates, decomposes, and produces plans, then delegates every concrete change via invoke_agent to fast-puppy / code-puppy. All execution is delegated and verified, never performed by the planner itself.
• Cancelled sub-agent status. Added a distinct cancelled status (🚫) to the subagent console so a user-cancelled sub-agent (Ctrl-X) no longer renders as a green "completed" row. asyncio.CancelledError is now handled explicitly in invoke_agent and re-raised so cancellation still propagates.
• Updated the orchestrator delegation matrix, AGENTS.md, README.md, and tests to reflect the read-only planning-agent contract.