M2.8: switch over to the new loop

nisse-dev now runs only the conversational loop. The gated state machine
it was built alongside is gone:

- Removed control.py, planner.py, executor.py, approvals.py, gates.py
  (command_form moves to loop/reader.py), publish.py and poller.py, the
  old assembly in agent.py (its shared helpers move to loop/build.py),
  the store's state-machine view (get_state, transition), their tests,
  the old end-to-end and live planning/milestone/gate tests, and
  specs/orchestrator.qnt with its scenarios.
- Roles are driver, helper, expert and classifier; driver is required.
  loop:, roles.planner, roles.executor and tuning.executor are refused
  with what to use instead; tuning.driver takes the turn cap and failure
  limit.
- The benchmark and the capability matrix measure the driver: the
  loop's own system prompt and tools, the task's plan as the agreed
  restatement. Task plans end with finish_milestone, so earlier runs
  show as (old); stored runs' executor tuning reads as the driver's.
- A delegation on the loop records what its helper's alias resolved to
  (L9), as the old path's did.
- The dump shows a work item's revision and what it waits for.
- Behaviour the old tests covered and the loop shares stays covered:
  driver runs that fail on a model call, stop mid-turn, reset the
  failure count; go-aheads ignoring case and punctuation; a request too
  big to fit is never sent; the assembly tests, now on build_loop_agent.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPQ14L3LikyefCMFBqEbKE

nisse-dev.example.yaml

@@ -41,14 +41,11 @@ llm:                                  # L9: LiteLLM is the only LLM destination
   request_timeout_s: 600
 
 roles:                                # L9: role -> LiteLLM model alias
-  executor: qwen3.8-27b         # the local tier: best executor in the benchmark (PR #55)
-  planner: claude-opus-5-5      # high-end judgement: plans a weaker executor follows
-  helper: claude-opus-5-5     # takes over what the executor got stuck on
-  expert: claude-haiku-4-5  # one question at a time, no tools: cheap is enough
-  # The new loop's roles (loop: new): unset, driver is the planner's model and
-  # classifier the expert's. Each work item pins the mapping when it opens.
-  # driver: claude-opus-5-5     # drives the loop: talks, restates, works
-  # classifier: claude-haiku-4-5  # reads plain-language go-aheads (later: actions, L4)
+  # Each work item pins the mapping when it opens.
+  driver: claude-opus-5-5       # drives the loop: talks, restates, works
+  helper: claude-opus-5-5       # takes over what the driver got stuck on
+  expert: claude-haiku-4-5      # one question at a time, no tools: cheap is enough
+  # classifier: claude-haiku-4-5  # reads go-aheads (later: actions, L4); unset, expert's
 
 # Capability profiles (L9), from benchmarks: what one role is told about
 # another (never a model's name). Optional; a model without one is briefed as
@@ -83,8 +80,8 @@ gitea:                                # D4, D5
 # These are the defaults; the section can be left out entirely. The file is
 # read at startup, so a change takes effect on the next restart.
 tuning:
-  executor:
-    max_turns: 40            # model calls per milestone before it stops as capped
+  driver:
+    max_turns: 40            # model calls per driver run before it stops as capped
     failure_limit: 2         # consecutive failed commands before escalating (L9)
   expert:
     consult_budget: 3        # ask_expert calls per milestone (L9)