Add the delegation harness (A13) — step 7b

A frontier model receives a scoped sub-task, works autonomously with
full tool access, and hands back; the local loop reads the handback
note and the file state, never the reasoning.

- Branch at delegation start, and abort discards it. That required
  committing each turn's work onto the branch: without commits,
  deleting a branch discards nothing, so "abort discards the work"
  was a comforting phrase rather than a fact. The caller's own
  in-flight changes are committed to their branch first, so an abort
  cannot destroy work nobody delegated
- Hard caps on turns and wall clock; a breach is a defined failure
  return, and its result is not usable, so the caller gates rather
  than resuming on a half-edited tree
- Every event is checkpointed as it arrives, so a crash mid-delegation
  leaves the branch at a known commit and a truthful transcript
- Handback is validated locally: blank fields or a non-boolean success
  flag are refused and the delegation continues rather than accepting
  a useless note

Two failure modes found by running it against a real model:

- A success claim with nothing changed was accepted. The handback plus
  file state is the entire interface back, so a note describing work
  that does not exist is worse than no note. Success now requires a
  successful mutating tool call; reporting failure still does not,
  since "this is impossible" is a legitimate finding
- The delegate invented the absolute path /workspace, wrote there, ran
  its tests there, and handed back truthfully — with the repo empty
  and git seeing nothing. Writes outside the workspace are now refused
  with a message naming the real root, and both prompts state where
  the workspace is instead of leaving the model to guess. This is not
  sandboxing: work outside the repo is invisible to git, so the
  milestone would publish an empty PR

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

tests/integration/test_delegation_live.py

@@ -0,0 +1,89 @@
+"""A real delegation over the Anthropic passthrough: scoped sub-task in,
+working code and a structured handback out."""
+
+import io
+import os
+from pathlib import Path
+
+import pytest
+
+from nisse_dev.delegation import Caps, Delegation
+from nisse_dev.envfile import load_env_file
+from nisse_dev.git import GitRepo
+from nisse_dev.llm import AnthropicPassthroughClient
+from nisse_dev.oplog import OpLog
+from nisse_dev.state import StateStore
+from nisse_dev.tools import Workspace
+
+load_env_file(Path(__file__).resolve().parents[2] / ".env")
+
+SENTINEL = "NISSE_LIVE_PLANNER_MODEL"
+
+pytestmark = [
+    pytest.mark.integration,
+    pytest.mark.skipif(
+        not os.environ.get(SENTINEL),
+        reason=f"no live frontier route configured ({SENTINEL} unset)",
+    ),
+]
+
+BRIEF = """Create `slugify.py` in the workspace root containing a function
+`slugify(text)` that lowercases the text and replaces every run of
+non-alphanumeric characters with a single hyphen, with no leading or trailing
+hyphen. Then create `test_slugify.py` with at least two assertions covering
+it, and run `python -m pytest test_slugify.py -q` until it passes."""
+
+
+def build(tmp_path: Path, caps: Caps) -> tuple[Delegation, GitRepo, StateStore]:
+    repo = GitRepo(tmp_path / "work")
+    repo.init()
+    repo.configure_identity("nisse-dev-testing", "n@t.test")
+    (repo.root / "README.md").write_text("sandbox\n")
+    repo.commit_all("seed")
+    store = StateStore(tmp_path / "state.db", oplog=OpLog("nisse-dev", io.StringIO()))
+    delegation = Delegation(
+        AnthropicPassthroughClient.from_env(),
+        store,
+        Workspace(repo.root, timeout_s=60),
+        repo,
+        model=os.environ[SENTINEL],
+        caps=caps,
+    )
+    return delegation, repo, store
+
+
+def test_delegate_completes_a_scoped_subtask(tmp_path: Path) -> None:
+    delegation, repo, _store = build(tmp_path, Caps(turns=12, wall_clock_s=300.0))
+
+    result = delegation.run(brief=BRIEF, branch="live/delegation-1")
+
+    assert result.usable, f"delegation did not hand back: {result.status} {result.note}"
+    assert (repo.root / "slugify.py").exists()
+
+    # The handback is the entire interface back, so it must actually say
+    # something in each part rather than be structurally present but empty.
+    handback = result.handback
+    assert handback is not None
+    assert len(handback.changed) > 10
+    assert len(handback.now_true) > 10
+    assert len(handback.next) > 5
+
+    # The delegate's own work is on its branch, and it really runs.
+    assert repo.current_branch() == "live/delegation-1"
+    check = Workspace(repo.root, timeout_s=60).run_command(
+        "python -m pytest test_slugify.py -q"
+    )
+    assert check.success, f"delegate's own tests do not pass: {check.result[:400]}"
+
+
+def test_a_cap_breach_discards_the_work(tmp_path: Path) -> None:
+    # One turn cannot finish the brief, so this exercises the abort path
+    # against a real model rather than a scripted one.
+    delegation, repo, _ = build(tmp_path, Caps(turns=1, wall_clock_s=120.0))
+
+    result = delegation.run(brief=BRIEF, branch="live/delegation-2")
+
+    assert not result.usable
+    assert result.status == "capped"
+    assert repo.current_branch() == "main"
+    assert not (repo.root / "slugify.py").exists()