fix(prompt+tools): inject A2A/HMA docs + unify LangChain tool names with MCP

[HongmingWang-Rabbit]

Summary

Workers were registering platform tools (`delegate_task`, `delegate_task_async`, `list_peers`, `check_task_status`, `send_message_to_user`, `commit_memory`, `recall_memory`) but the `build_system_prompt()` assembly never included documentation for any of them. The instruction-text functions `get_a2a_instructions()` and `get_hma_instructions()` exist in `executor_helpers.py` and have unit tests, but were never called from any production code path — workers received `system-prompt.md` content only and saw the tools as bare names with no usage guidance.

Symptom: agents called `commit_memory` and `delegate_task` without knowing they were platform tools. They worked when the agent guessed the API correctly and silently failed when the agent didn't.

Fix

`build_system_prompt()` now appends both instruction sets between the Skills section and the Peers section. The placement is intentional — A2A docs explain how to call `delegate_task`; the peer list is the data that `delegate_task` operates over, so the docs precede the peer table.

New parameter `a2a_mcp: bool = True` lets adapters opt into the CLI subprocess variant of the A2A instructions for runtimes without MCP support (ollama, custom CLI runtimes). Default `True` covers the MCP-capable majority (claude-code, hermes, langchain, crewai). Adapter callers don't need to change unless they specifically need CLI mode.

Tests

4 new regression tests in `test_prompt.py`:

• A2A MCP variant injection (default)
• A2A CLI variant injection (`a2a_mcp=False`, with MCP-only fields absent)
• HMA instruction injection
• A2A docs precede peer list ordering

Full workspace suite green: 1223 passed, 2 xfailed.

Test plan

• `pytest workspace/tests/test_prompt.py` — 22 pass (18 existing + 4 new)
• `WORKSPACE_ID=test pytest workspace/tests/` — 1223 pass, 2 xfailed
• CI on this PR
• Once merged + workspaces redeploy: confirm Design Director / worker prompts now include the A2A and HMA sections (verifiable via runtime log of system prompt or by asking an agent for its system prompt)

🤖 Generated with Claude Code