Implement REIN-A-0002 ops_run claim loop and approach registry.

Add activity-core ops_run client, approach selection (FI/Binky/mail/agent),
claim-loop worker with lease heartbeat, CLI run --from-ops-run and claim-loop,
install units, and docs demoting issue-core to legacy external tickets.
T05 timer cutover remains operator after five clean cycles.

tests/test_claim_loop.py

@@ -0,0 +1,97 @@
+"""Claim loop process_one tests (REIN-A-0002-T03)."""
+
+from __future__ import annotations
+
+from unittest.mock import MagicMock, patch
+
+from rein_aharness.approaches import ApproachResult, APPROACH_FI_RESEARCH_BRIEF
+from rein_aharness.claim_loop import process_one, poll_peek
+from rein_aharness.ops_run_client import OpsRun, OpsRunConfig, ActivityCoreOpsClient
+
+
+def _claimed_run() -> OpsRun:
+    return OpsRun(
+        id="run-1",
+        activity_definition_id="def",
+        idempotency_key="k",
+        target_repo="freedom-intelligence",
+        title="FI daily",
+        description="d",
+        labels=["automated", "research-brief"],
+        state="claimed",
+        claim_owner="worker-1",
+        attempt=1,
+    )
+
+
+def test_process_one_empty() -> None:
+    client = MagicMock(spec=ActivityCoreOpsClient)
+    client.config = OpsRunConfig(worker_id="w", lease_seconds=90)
+    client.claim.return_value = []
+    r = process_one(client)
+    assert r.empty is True
+    assert r.claimed is False
+
+
+def test_process_one_success_completes() -> None:
+    client = MagicMock(spec=ActivityCoreOpsClient)
+    client.config = OpsRunConfig(worker_id="w", lease_seconds=90)
+    client.claim.return_value = [_claimed_run()]
+    client.complete.return_value = OpsRun(
+        id="run-1",
+        activity_definition_id="def",
+        idempotency_key="k",
+        target_repo="freedom-intelligence",
+        title="FI daily",
+        description="",
+        state="succeeded",
+        labels=["automated", "research-brief"],
+    )
+    ar = ApproachResult(
+        ok=True,
+        approach=APPROACH_FI_RESEARCH_BRIEF,
+        result={"path": "briefs/x.md"},
+        reason="ok",
+    )
+    with patch("rein_aharness.claim_loop.execute_approach", return_value=ar):
+        r = process_one(client)
+    assert r.claimed is True
+    assert r.ok is True
+    assert r.approach == APPROACH_FI_RESEARCH_BRIEF
+    client.complete.assert_called_once()
+    client.fail.assert_not_called()
+
+
+def test_process_one_failure_reopens() -> None:
+    client = MagicMock(spec=ActivityCoreOpsClient)
+    client.config = OpsRunConfig(worker_id="w", lease_seconds=90)
+    client.claim.return_value = [_claimed_run()]
+    client.fail.return_value = OpsRun(
+        id="run-1",
+        activity_definition_id="def",
+        idempotency_key="k",
+        target_repo="freedom-intelligence",
+        title="t",
+        description="",
+        state="open",
+        labels=["automated", "research-brief"],
+    )
+    ar = ApproachResult(
+        ok=False,
+        approach=APPROACH_FI_RESEARCH_BRIEF,
+        reason="llm timeout",
+        reopen=True,
+    )
+    with patch("rein_aharness.claim_loop.execute_approach", return_value=ar):
+        r = process_one(client)
+    assert r.ok is False
+    client.fail.assert_called_once()
+    assert client.fail.call_args.kwargs["reopen"] is True
+
+
+def test_poll_peek() -> None:
+    client = MagicMock(spec=ActivityCoreOpsClient)
+    client.list_open.return_value = [_claimed_run()]
+    rows = poll_peek(client)
+    assert len(rows) == 1
+    assert rows[0]["approach"] == APPROACH_FI_RESEARCH_BRIEF