Add Gitea client and git operations (B2) — step 6a, part 1

The standalone half of the Gitea layer; orchestrator wiring follows
once the executor loop lands, to avoid colliding with it in
control.py.

- gitea.py: GiteaClient over httpx — open PRs, list and post issue
  comments, close PRs. find_pull_request is the A3 external-truth
  query that makes opening a PR idempotent across a crash, and it
  checks closed PRs too, since a crash after opening must not be
  answered with "nothing is open, so open another"
- pull_request_reconciler: an unreachable Gitea returns None rather
  than a guess, so the agent gates to the human instead of risking a
  duplicate side effect
- git.py: branch, commit, push for the workspace. The token is passed
  per-invocation rather than stored as a remote, so it never lands in
  .git/config, and anything raised is scrubbed of it
- commit_all returns None when there is nothing to commit: an empty
  milestone is a fact to report, not an error
- Live test does the real round trip against the sandbox repo and
  cleans up after itself

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

nisse-dev/tests/test_gitea.py

@@ -0,0 +1,175 @@
+import json
+
+import httpx
+import pytest
+
+from nisse_dev.gitea import (
+    Comment,
+    GiteaClient,
+    GiteaError,
+    pull_request_reconciler,
+)
+from nisse_dev.state import Intent
+
+INTENT = Intent(
+    id=1,
+    kind="open_pr",
+    payload={"branch": "milestone-1"},
+    status="pending",
+    created_at="t",
+    resolved_at=None,
+)
+
+
+def client(handler) -> GiteaClient:
+    return GiteaClient(
+        "https://gitea.test/", "tok", transport=httpx.MockTransport(handler)
+    )
+
+
+def pr_json(number: int, head: str, state: str = "open") -> dict:
+    return {
+        "number": number,
+        "state": state,
+        "head": {"ref": head},
+        "html_url": f"https://gitea.test/o/r/pulls/{number}",
+    }
+
+
+def test_open_pull_request_posts_expected_body() -> None:
+    seen: dict = {}
+
+    def handler(request: httpx.Request) -> httpx.Response:
+        seen["url"] = str(request.url)
+        seen["auth"] = request.headers.get("authorization")
+        seen["body"] = json.loads(request.content)
+        return httpx.Response(201, json=pr_json(7, "milestone-1"))
+
+    pr = client(handler).open_pull_request(
+        "o/r", head="milestone-1", base="main", title="T", body="B"
+    )
+    assert seen["url"] == "https://gitea.test/api/v1/repos/o/r/pulls"
+    assert seen["auth"] == "token tok"
+    assert seen["body"] == {
+        "head": "milestone-1",
+        "base": "main",
+        "title": "T",
+        "body": "B",
+    }
+    assert pr.number == 7
+    assert pr.head == "milestone-1"
+
+
+def test_find_pull_request_matches_head_branch() -> None:
+    def handler(request: httpx.Request) -> httpx.Response:
+        if request.url.params.get("state") == "open":
+            return httpx.Response(200, json=[pr_json(3, "other")])
+        return httpx.Response(200, json=[])
+
+    assert client(handler).find_pull_request("o/r", "milestone-1") is None
+
+
+def test_find_pull_request_also_checks_closed() -> None:
+    # A crash after opening must not be answered with "nothing open, open
+    # another" — the effect already happened.
+    def handler(request: httpx.Request) -> httpx.Response:
+        if request.url.params.get("state") == "open":
+            return httpx.Response(200, json=[])
+        return httpx.Response(200, json=[pr_json(4, "milestone-1", "closed")])
+
+    found = client(handler).find_pull_request("o/r", "milestone-1")
+    assert found is not None
+    assert found.number == 4
+
+
+def test_error_status_raises_gitea_error() -> None:
+    handler = lambda request: httpx.Response(403, text="forbidden")
+    with pytest.raises(GiteaError, match="403"):
+        client(handler).whoami()
+
+
+def test_list_and_post_comments() -> None:
+    def handler(request: httpx.Request) -> httpx.Response:
+        if request.method == "POST":
+            return httpx.Response(
+                201,
+                json={
+                    "id": 9,
+                    "user": {"login": "don"},
+                    "body": "hi",
+                    "created_at": "t",
+                },
+            )
+        return httpx.Response(
+            200,
+            json=[
+                {
+                    "id": 8,
+                    "user": {"login": "don"},
+                    "body": "approve rev-1",
+                    "created_at": "t",
+                }
+            ],
+        )
+
+    c = client(handler)
+    assert c.list_comments("o/r", 1) == [
+        Comment(id=8, author="don", body="approve rev-1", created_at="t")
+    ]
+    assert c.post_comment("o/r", 1, "hi").id == 9
+
+
+def test_list_comments_passes_since() -> None:
+    seen: dict = {}
+
+    def handler(request: httpx.Request) -> httpx.Response:
+        seen["since"] = request.url.params.get("since")
+        return httpx.Response(200, json=[])
+
+    client(handler).list_comments("o/r", 1, since="2026-09-07T00:00:00Z")
+    assert seen["since"] == "2026-09-07T00:00:00Z"
+
+
+def test_from_env_requires_config() -> None:
+    with pytest.raises(GiteaError, match="NISSE_GITEA_URL"):
+        GiteaClient.from_env({})
+
+
+# --- reconciler (A3 external truth) --------------------------------------
+
+
+def test_reconciler_reports_existing_pr_as_done() -> None:
+    handler = lambda request: httpx.Response(
+        200,
+        json=[pr_json(5, "milestone-1")]
+        if request.url.params.get("state") == "open"
+        else [],
+    )
+    assert pull_request_reconciler(client(handler), "o/r")(INTENT) is True
+
+
+def test_reconciler_reports_missing_pr_as_not_done() -> None:
+    handler = lambda request: httpx.Response(200, json=[])
+    assert pull_request_reconciler(client(handler), "o/r")(INTENT) is False
+
+
+def test_unreachable_gitea_is_unverifiable_not_a_guess() -> None:
+    def handler(request: httpx.Request) -> httpx.Response:
+        raise httpx.ConnectError("refused")
+
+    # None gates to the human: a delayed decision is cheap, a duplicate PR
+    # is not.
+    assert pull_request_reconciler(client(handler), "o/r")(INTENT) is None
+
+
+def test_intent_without_a_branch_is_unverifiable() -> None:
+    handler = lambda request: httpx.Response(200, json=[])
+    blank = Intent(
+        id=2,
+        kind="open_pr",
+        payload={},
+        status="pending",
+        created_at="t",
+        resolved_at=None,
+    )
+    assert pull_request_reconciler(client(handler), "o/r")(blank) is None