Fix: open findings cleanup (#122)

* refactor(usage): remove the unconsumed per-agent USAGE_UPDATE event

USAGE_UPDATE was published per active agent each sweep, bridged, and
broadcast to /ws/system, but no panel client ever consumed it — the
dashboard reads only the aggregate USAGE_SNAPSHOT. Every emission was
wasted event-bus and WebSocket traffic.

Drop the UsageUpdate payload, publish_usage_update and its throttle, the
EventType member, and the bridge subscription. Keep USAGE_SNAPSHOT, which
already carries the per-agent breakdown, so no live data is lost.

* refactor(prompter): remove the legacy local-LLM HTTP endpoints

The panel uses only the live SDK-intake path (/prompter/live/*); the legacy
/prompter/chat, /draft and /sessions/* endpoints — backed by the local Ollama
LLM with hardcoded prompts — had no remaining caller. Remove the router, its
mount in app.py, and its integration test. The live router and the shared
draft-confirmation service are untouched.

* refactor(prompter): drop the dead legacy local-LLM service + schemas

With the legacy HTTP endpoints gone, the local-LLM chat/draft/session methods,
their prompt constants, the ConfirmOverrides/TurnResult dataclasses, and the
entire prompter schema module had no production caller (only their own tests).
Remove them, keeping the live-intake path: create_task_from_draft /
confirm_live_draft, the enum/priority/team coercion, and the pure
description/readiness helpers.

* refactor(agents): stop granting the Task sub-agent tool to roles

Every agent role was granted the built-in Task tool, but no role prompt or
workflow uses it and there are no custom sub-agent definitions — so a Task call
only spawns a context-blind generic sub-agent that burns budget (ToolSearch,
the comment's stated use, is MCP-only and not callable in agent containers).

Drop Task from all three grant points in lockstep: the --tools spawn flag and
both _ROLE_BUILTIN_TOOLS maps (system-prompt + briefing layers), with a
regression guard added to each layer's test.

---------

Co-authored-by: Renn F <rennf93@users.noreply.github.com>

tests/unit/runtime/test_briefing_tool_load_block.py

@@ -68,6 +68,26 @@ def test_pm_blocks_exclude_edit_and_write() -> None:
         assert "Write" not in names, f"{role} must not list Write"
 
 
+def test_no_role_block_lists_the_task_subagent_tool() -> None:
+    """Task (sub-agent dispatch) is dropped from the briefing tool grant.
+
+    No role uses Task and there are no custom sub-agent definitions, so it only
+    spawns a context-blind generic sub-agent that burns budget.
+    """
+    for role in (
+        "developer",
+        "documenter",
+        "qa",
+        "main_pm",
+        "cell_pm",
+        "product_owner",
+        "head_marketing",
+        "auditor",
+    ):
+        names = _tool_names(_orch()._build_tool_load_block(role))
+        assert "Task" not in names, f"{role} must not list Task: {names}"
+
+
 def test_unknown_role_returns_empty() -> None:
     assert _orch()._build_tool_load_block("nonexistent") == ""