Agents can hand work to agents: dispatch_agent

A schedule is a time trigger, and only the first step of a pipeline is really
waiting on time — every later step waits on the previous step's result. Modeling
"watch a source -> write a spec -> implement it" as three schedules made each fire
blind: on a quiet day the coding agent still spawned, paid a full model run to find
there was nothing to do, and left an empty run in Activity.

So an agent can start the next step itself. `dispatch_agent` (a tool on the bundled
MCP server, and on the pi bridge through the same --call seam) enqueues an ordinary
spawn command in the agent's own project, tagged requested_by=agent:<id> — so a
handoff is visible in Activity with no new surface to build.

- Project-scoped by construction: project_id is read from the spawn environment and
  never from the tool arguments.
- Bounded rather than gated: MAX_DISPATCH_PER_RUN counts the command rows the agent
  already wrote; MAX_DISPATCH_DEPTH rides in the spawn payload and is recovered by
  spawn._dispatch_depth, so a chain keeps its place across a resume and a cycle
  terminates instead of fanning out.
- New scout and planner roles, with built-in skills (handler-scout, handler-planner,
  handler-dispatch) carrying the judgment code can't: dedupe against a memory-note
  watermark, treat "nothing new" as a complete run, and write a task the receiving
  cold-start agent can act on.
- A scout ending on a clean tree skips the test gate and records the new
  tests_status='skipped' (migration 0017, additive CHECK widening). The gate promises
  `done` means tests passed for the work that shipped; nothing shipped.

Rejected a `condition` field on schedules: "is this paper new and does it matter
here?" is a semantic judgment, so it belongs to a model, not a scheduler column. The
scout is the condition; dispatch is how it reports true — one mechanism that covers
future pipelines too.

426 tests (14 new for dispatch, 3 for the gate exemption).

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HcbDevyMcJWE6qPA56C7mZ

tests/test_memory.py

@@ -181,8 +181,10 @@ def test_mcp_protocol_basics(seeded):
     assert handle_message(server, {"jsonrpc": "2.0", "method": "notifications/initialized"}) is None
     assert _rpc(server, "resources/list")["error"]["code"] == -32601
     tools = _rpc(server, "tools/list")["result"]["tools"]
+    # The bundled server's whole surface: the memory tools plus dispatch (tested in
+    # tests/test_dispatch.py), which shares this transport and identity contract.
     assert {t["name"] for t in tools} == {
-        "memory_search", "memory_get", "memory_save", "memory_link",
+        "memory_search", "memory_get", "memory_save", "memory_link", "dispatch_agent",
     }