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/src/nisse_dev/bench/tasks/fix-bug/task.yaml

@@ -9,4 +9,4 @@ plan: |
   3. Fix `total_value` so that each item contributes its unit price times its
      quantity.
   4. Run `python -m pytest -q` until every test passes.
-  5. Call finish.
+  5. Call finish_milestone, with final yes.

nisse-dev/src/nisse_dev/bench/tasks/long-milestone/task.yaml

@@ -37,4 +37,4 @@ plan: |
      then the same with `list --overdue`, which must print
      `[!] 1 Pay rent (due 2026-10-01)`. Delete /tmp/tracker-check.json
      before and after.
-  9. Call finish.
+  9. Call finish_milestone, with final yes.

nisse-dev/src/nisse_dev/bench/tasks/long-output/task.yaml

@@ -9,4 +9,4 @@ plan: |
      (NNN mod 25) / 100. Correct only the failing region's entry; leave every
      other line as it is.
   3. Run `python -m pytest -q` until every test passes.
-  4. Call finish.
+  4. Call finish_milestone, with final yes.

nisse-dev/src/nisse_dev/bench/tasks/multi-file/task.yaml

@@ -13,4 +13,4 @@ plan: |
      using pytest's capsys fixture.
   4. Run `python -m pytest -q` until every test passes, and check that
      `python -m greeter --shout Bob` prints `HELLO, BOB!`.
-  5. Call finish.
+  5. Call finish_milestone, with final yes.

nisse-dev/src/nisse_dev/bench/tasks/refactor-rename/task.yaml

@@ -15,4 +15,4 @@ plan: |
      are different functions and keep their names. Change no behaviour.
   4. Update the tests under `tests/` to use the new name, and run
      `python -m pytest -q` until every test passes.
-  5. Call finish.
+  5. Call finish_milestone, with final yes.

nisse-dev/src/nisse_dev/bench/tasks/spec-parser/task.yaml

@@ -12,4 +12,4 @@ plan: |
      invalid input for each of the eight rules.
   4. Run `python -m pytest -q test_durations.py`, and fix `durations.py`
      until every test passes.
-  5. Call finish.
+  5. Call finish_milestone, with final yes.

nisse-dev/src/nisse_dev/bench/tasks/trace-bug/task.yaml

@@ -18,4 +18,4 @@ plan: |
      `invoicing/currency.py` have up to six decimal places (JPY is 0.006712),
      and no step may round a rate or fraction to fewer places than that.
   4. Run `python -m pytest -q` until every test passes.
-  5. Call finish.
+  5. Call finish_milestone, with final yes.

nisse-dev/src/nisse_dev/bench/tasks/write-function/task.yaml

@@ -10,4 +10,4 @@ plan: |
      "a--b" -> "a-b"; "" -> "".
   3. Create `test_slugify.py` with pytest tests covering the four examples.
   4. Run `python -m pytest -q test_slugify.py`, and fix anything until it passes.
-  5. Call finish.
+  5. Call finish_milestone, with final yes.