Bootstrap rein-openweights: minimal agentic loop over OpenRouter (REIN-OW-WP-0001)

Implements T01-T04:
- tools.py: green-commit-only-equivalent tool surface (read/write/edit/
  glob/grep + git status/diff/log/add+commit), path-traversal guarded.
- openrouter_client.py: own minimal chat-completions client — llm-connect's
  OpenRouterAdapter takes a single prompt string and never surfaces
  tool_calls, so it can't drive a multi-turn tool-calling loop without a
  breaking change to its frozen Core ABC. llm-connect stays an optional
  dependency (pyproject.toml), not load-bearing.
- loop.py: plan -> tool call -> observe -> repeat, budget- and
  turn-bounded, tool errors reported back to the model instead of
  crashing the loop.
- credentials.py: own OpenBao AppRole/ambient-token acquisition, per
  glas-harness ADR-002 (Option B) — glas-harness does not broker this.
- runner.py/hub.py: commit-verified success criterion + State Hub
  progress/token reporting, mirroring rein-aharness's model.

26 tests, all mocked at the httpx/subprocess boundary — no real
OpenRouter or OpenBao calls made. T05 (Forgejo repo creation) stays
open, deferred to the operator.

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

tests/test_loop.py

@@ -0,0 +1,118 @@
+import subprocess
+from unittest.mock import MagicMock
+
+from rein_openweights.budget import BudgetTracker
+from rein_openweights.loop import run_loop
+
+
+def _init_repo(tmp_path):
+    subprocess.run(["git", "init", "-q"], cwd=tmp_path, check=True)
+    subprocess.run(["git", "config", "user.email", "t@example.com"], cwd=tmp_path, check=True)
+    subprocess.run(["git", "config", "user.name", "t"], cwd=tmp_path, check=True)
+    subprocess.run(["git", "commit", "-q", "--allow-empty", "-m", "init"], cwd=tmp_path, check=True)
+    return tmp_path
+
+
+def _response(message, total_tokens=100):
+    return {
+        "choices": [{"message": message}],
+        "usage": {"total_tokens": total_tokens},
+    }
+
+
+def test_run_loop_executes_tool_call_then_finishes(tmp_path):
+    repo = _init_repo(tmp_path)
+    client = MagicMock()
+    client.chat.side_effect = [
+        _response(
+            {
+                "role": "assistant",
+                "content": None,
+                "tool_calls": [
+                    {
+                        "id": "call_1",
+                        "function": {
+                            "name": "write_file",
+                            "arguments": '{"path": "NOTES.md", "content": "hi"}',
+                        },
+                    }
+                ],
+            }
+        ),
+        _response(
+            {
+                "role": "assistant",
+                "tool_calls": [
+                    {
+                        "id": "call_2",
+                        "function": {
+                            "name": "git_add_commit",
+                            "arguments": '{"message": "add notes"}',
+                        },
+                    }
+                ],
+            }
+        ),
+        _response({"role": "assistant", "content": "All set. DONE"}),
+    ]
+
+    result = run_loop(client, repo, "t", "d", budget=BudgetTracker(total=10_000))
+
+    assert result.finished is True
+    assert result.turns == 3
+    assert (repo / "NOTES.md").read_text() == "hi"
+    log = subprocess.run(
+        ["git", "-C", str(repo), "log", "--oneline"], capture_output=True, text=True
+    ).stdout
+    assert "add notes" in log
+
+
+def test_run_loop_stops_when_budget_exceeded(tmp_path):
+    repo = _init_repo(tmp_path)
+    client = MagicMock()
+    client.chat.return_value = _response({"role": "assistant", "content": "still going"}, total_tokens=100)
+
+    result = run_loop(client, repo, "t", "d", budget=BudgetTracker(total=50))
+
+    assert result.error is not None
+    assert "budget" in result.error.lower()
+
+
+def test_run_loop_stops_at_max_turns(tmp_path):
+    repo = _init_repo(tmp_path)
+    client = MagicMock()
+    client.chat.return_value = _response(
+        {
+            "role": "assistant",
+            "tool_calls": [
+                {"id": "c", "function": {"name": "git_status", "arguments": "{}"}}
+            ],
+        }
+    )
+
+    result = run_loop(client, repo, "t", "d", max_turns=2)
+
+    assert result.turns == 2
+    assert result.error == "max_turns exceeded"
+
+
+def test_run_loop_reports_tool_error_without_crashing(tmp_path):
+    repo = _init_repo(tmp_path)
+    client = MagicMock()
+    client.chat.side_effect = [
+        _response(
+            {
+                "role": "assistant",
+                "tool_calls": [
+                    {"id": "c", "function": {"name": "read_file", "arguments": '{"path": "missing.txt"}'}}
+                ],
+            }
+        ),
+        _response({"role": "assistant", "content": "done anyway DONE"}),
+    ]
+
+    result = run_loop(client, repo, "t", "d")
+
+    assert result.finished is True
+    tool_messages = [m for m in result.transcript if m.get("role") == "tool"]
+    assert "error" in tool_messages[0]["content"]