feat(forge): forge library layer for native integration (PRD chunks 1-3, 5)

Implements the bot-bottle side of the forge-native PRD that is
self-contained in this repo (the forge sidecar and orchestrate command
belong to the separate bot-bottle-orchestrator, a PRD non-goal):

- contrib/forge/base.py: Forge ABC + ScopedForge enforcing the
  read-anywhere / write-scoped model (writes rejected outside the
  assigned issue/PRs via ForgeScopeError).
- contrib/gitea/client.py: GiteaClient (stdlib-only HTTP, mirrors the
  deploy-key provisioner) + GiteaForge. Token held by the caller (the
  sidecar), not injected by cred-proxy.
- contrib/gitea/forge_state.py: ForgeState dataclass + atomic
  read/write/delete/all under ~/.bot-bottle/forge/<owner>/<repo>/.
- contrib/gitea/provenance.py: build_provenance_footer — collapsed
  markdown audit footer; watchdog/gitleaks/egress rendering.
- cli/resume.py: `resume --headless --prompt` reusing the shipped
  assume_yes + headless_prompt launch core (the new half of chunk 1).

47 new unit tests; pylint 9.98/10, pyright clean. Forge sidecar (chunk
4), orchestrate command (chunk 6), and forge_env plumbing are deferred:
their only consumer is the separate orchestrator and they are untestable
in isolation here.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WL77TgFxKbs3cidGMG9dz7

tests/unit/test_contrib_gitea_client.py

@@ -0,0 +1,131 @@
+"""Unit: GiteaClient + GiteaForge (PRD forge-native-integration)."""
+
+from __future__ import annotations
+
+import json
+import unittest
+import urllib.error
+from io import BytesIO
+from unittest.mock import MagicMock, patch
+
+from bot_bottle.contrib.gitea.client import GiteaClient, GiteaForge
+
+
+def _client() -> GiteaClient:
+    return GiteaClient(
+        api_url="https://gitea.example.com/api/v1",
+        owner="didericis",
+        repo="bot-bottle",
+        token="test-token",
+    )
+
+
+def _resp(body, status: int = 200) -> MagicMock:
+    resp = MagicMock()
+    resp.read.return_value = json.dumps(body).encode() if body is not None else b""
+    resp.status = status
+    resp.__enter__ = lambda s: s
+    resp.__exit__ = MagicMock(return_value=False)
+    return resp
+
+
+def _http_error(code: int, body: str = "") -> urllib.error.HTTPError:
+    return urllib.error.HTTPError(
+        url="http://x", code=code, msg="err", hdrs=None,  # type: ignore[arg-type]
+        fp=BytesIO(body.encode()),
+    )
+
+
+_URLOPEN = "bot_bottle.contrib.gitea.client.urllib.request.urlopen"
+
+
+class TestOrgMembership(unittest.TestCase):
+    def test_member_returns_true_on_2xx(self):
+        with patch(_URLOPEN, return_value=_resp(None, 204)) as m:
+            self.assertTrue(_client().is_org_member("bot-bottle", "alice"))
+        req = m.call_args.args[0]
+        self.assertIn("/orgs/bot-bottle/members/alice", req.full_url)
+
+    def test_nonmember_returns_false_on_404(self):
+        with patch(_URLOPEN, side_effect=_http_error(404)):
+            self.assertFalse(_client().is_org_member("bot-bottle", "stranger"))
+
+    def test_other_http_error_raises(self):
+        with patch(_URLOPEN, side_effect=_http_error(403, "forbidden")):
+            with self.assertRaises(RuntimeError) as ctx:
+                _client().is_org_member("bot-bottle", "alice")
+        self.assertIn("403", str(ctx.exception))
+
+
+class TestForgeReads(unittest.TestCase):
+    def test_read_issue_maps_fields(self):
+        raw = {"number": 17, "title": "Bug", "body": "broken", "state": "open"}
+        with patch(_URLOPEN, return_value=_resp(raw)) as m:
+            issue = GiteaForge(_client()).read_issue(17)
+        self.assertEqual((17, "Bug", "broken", "open"),
+                         (issue.number, issue.title, issue.body, issue.state))
+        self.assertIn("/repos/didericis/bot-bottle/issues/17",
+                      m.call_args.args[0].full_url)
+
+    def test_read_issue_tolerates_null_body(self):
+        raw = {"number": 17, "title": "T", "body": None, "state": "open"}
+        with patch(_URLOPEN, return_value=_resp(raw)):
+            self.assertEqual("", GiteaForge(_client()).read_issue(17).body)
+
+    def test_read_comments_maps_user_login(self):
+        raw = [
+            {"id": 1, "user": {"login": "alice"}, "body": "hi"},
+            {"id": 2, "user": {"login": "bob"}, "body": "yo"},
+        ]
+        with patch(_URLOPEN, return_value=_resp(raw)):
+            comments = GiteaForge(_client()).read_comments(17)
+        self.assertEqual(["alice", "bob"], [c.user for c in comments])
+        self.assertEqual([1, 2], [c.id for c in comments])
+
+
+class TestForgeWrites(unittest.TestCase):
+    def test_post_comment_payload_and_url(self):
+        with patch(_URLOPEN, return_value=_resp(None, 201)) as m:
+            GiteaForge(_client()).post_comment(17, "done ✓")
+        req = m.call_args.args[0]
+        self.assertEqual("POST", req.method)
+        self.assertIn("/repos/didericis/bot-bottle/issues/17/comments", req.full_url)
+        self.assertEqual("done ✓", json.loads(req.data)["body"])
+
+    def test_update_description_patches_issue(self):
+        with patch(_URLOPEN, return_value=_resp(None, 200)) as m:
+            GiteaForge(_client()).update_description(17, "edited")
+        req = m.call_args.args[0]
+        self.assertEqual("PATCH", req.method)
+        self.assertTrue(req.full_url.endswith("/issues/17"))
+        self.assertEqual("edited", json.loads(req.data)["body"])
+
+    def test_auth_header_sent(self):
+        with patch(_URLOPEN, return_value=_resp(None, 201)) as m:
+            GiteaForge(_client()).post_comment(17, "x")
+        self.assertEqual("token test-token",
+                         m.call_args.args[0].headers["Authorization"])
+
+
+class TestPRHelpers(unittest.TestCase):
+    def test_get_pr_for_issue_returns_number_when_issue_is_pr(self):
+        raw = {"number": 18, "pull_request": {"merged": False}}
+        with patch(_URLOPEN, return_value=_resp(raw)):
+            self.assertEqual(18, GiteaForge(_client()).get_pr_for_issue(18))
+
+    def test_get_pr_for_issue_none_for_plain_issue(self):
+        raw = {"number": 17, "pull_request": None}
+        with patch(_URLOPEN, return_value=_resp(raw)):
+            self.assertIsNone(GiteaForge(_client()).get_pr_for_issue(17))
+
+    def test_is_pr_open_true_when_state_open(self):
+        with patch(_URLOPEN, return_value=_resp({"state": "open"})):
+            self.assertTrue(GiteaForge(_client()).is_pr_open(18))
+
+    def test_is_pr_open_false_when_closed(self):
+        with patch(_URLOPEN, return_value=_resp({"state": "closed"})):
+            self.assertFalse(GiteaForge(_client()).is_pr_open(18))
+
+
+if __name__ == "__main__":
+    unittest.main()