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

bot_bottle/contrib/gitea/client.py

@@ -0,0 +1,164 @@
+"""Gitea HTTP client + `GiteaForge` (PRD forge-native-integration, chunk 3).
+
+`GiteaClient` is the thin stdlib-only HTTP transport (mirrors
+`deploy_key_provisioner.py`: `urllib.request`, bounded timeouts,
+structured error bodies). `GiteaForge` adapts it to the provider-agnostic
+`Forge` surface.
+
+Unlike the option-2 design, the token is held here (the sidecar process
+owns it) and passed to the client directly — there is no agent-side
+cred-proxy route, because the agent never makes forge calls. The HTTP
+client is the one piece shared with `GiteaDeployKeyProvisioner`; the two
+are deliberately *not* unified behind a common abstract base (see the
+deferral note in the PRD).
+"""
+
+from __future__ import annotations
+
+import json
+import urllib.error
+import urllib.request
+from typing import Any
+
+from ..forge.base import Comment, Forge, Issue
+
+# Bound every Gitea call: a hung instance must not stall the sidecar.
+_API_TIMEOUT_SECS = 30
+
+
+class GiteaClient:
+    """Thin authenticated HTTP client for one repo's Gitea API.
+
+    `api_url` is the API base *including* `/api/v1` (matching the
+    `FORGE_GITEA_API` env var), e.g. `https://gitea.example.com/api/v1`.
+    """
+
+    def __init__(self, *, api_url: str, owner: str, repo: str, token: str) -> None:
+        self._api_url = api_url.rstrip("/")
+        self._owner = owner
+        self._repo = repo
+        self._token = token
+
+    # --- low-level request -------------------------------------------------
+
+    def _request(
+        self, method: str, path: str, *, body: dict[str, Any] | None = None
+    ) -> tuple[int, Any]:
+        """Issue an authenticated request. Returns `(status, parsed_json)`;
+        parsed_json is None when the response has no body. Raises
+        `RuntimeError` on any non-2xx except where callers special-case
+        the HTTPError themselves (membership 404)."""
+        url = f"{self._api_url}{path}"
+        data = json.dumps(body).encode() if body is not None else None
+        headers = {"Authorization": f"token {self._token}"}
+        if data is not None:
+            headers["Content-Type"] = "application/json"
+        req = urllib.request.Request(url, data=data, headers=headers, method=method)
+        with urllib.request.urlopen(req, timeout=_API_TIMEOUT_SECS) as resp:
+            raw = resp.read()
+            parsed = json.loads(raw) if raw else None
+            return resp.status, parsed
+
+    def _repo_path(self, suffix: str) -> str:
+        return f"/repos/{self._owner}/{self._repo}{suffix}"
+
+    # --- operations --------------------------------------------------------
+
+    def is_org_member(self, org: str, username: str) -> bool:
+        """GET /orgs/{org}/members/{username}: 2xx → member, 404 → not.
+        Other errors propagate so a misconfigured token fails loudly."""
+        url = f"{self._api_url}/orgs/{org}/members/{username}"
+        req = urllib.request.Request(
+            url, headers={"Authorization": f"token {self._token}"}, method="GET"
+        )
+        try:
+            with urllib.request.urlopen(req, timeout=_API_TIMEOUT_SECS):
+                return True
+        except urllib.error.HTTPError as exc:
+            if exc.code == 404:
+                return False
+            raise RuntimeError(
+                f"org membership check failed for {org}/{username}: "
+                f"HTTP {exc.code} — {_read_error_body(exc)}"
+            ) from exc
+
+    def get_issue(self, number: int) -> dict[str, Any]:
+        _status, body = self._request("GET", self._repo_path(f"/issues/{number}"))
+        return body or {}
+
+    def get_comments(self, number: int) -> list[dict[str, Any]]:
+        _status, body = self._request(
+            "GET", self._repo_path(f"/issues/{number}/comments")
+        )
+        return body or []
+
+    def post_comment(self, number: int, body: str) -> None:
+        self._request(
+            "POST",
+            self._repo_path(f"/issues/{number}/comments"),
+            body={"body": body},
+        )
+
+    def patch_issue_body(self, number: int, body: str) -> None:
+        self._request(
+            "PATCH", self._repo_path(f"/issues/{number}"), body={"body": body}
+        )
+
+    def get_pull(self, number: int) -> dict[str, Any]:
+        _status, body = self._request("GET", self._repo_path(f"/pulls/{number}"))
+        return body or {}
+
+
+class GiteaForge(Forge):
+    """`Forge` over a `GiteaClient`."""
+
+    def __init__(self, client: GiteaClient) -> None:
+        self._client = client
+
+    def read_issue(self, number: int) -> Issue:
+        raw = self._client.get_issue(number)
+        return Issue(
+            number=int(raw.get("number", number)),
+            title=str(raw.get("title", "")),
+            body=str(raw.get("body", "") or ""),
+            state=str(raw.get("state", "")),
+        )
+
+    def read_comments(self, number: int) -> list[Comment]:
+        return [
+            Comment(
+                id=int(c.get("id", 0)),
+                user=str((c.get("user") or {}).get("login", "")),
+                body=str(c.get("body", "") or ""),
+            )
+            for c in self._client.get_comments(number)
+        ]
+
+    def post_comment(self, number: int, body: str) -> None:
+        self._client.post_comment(number, body)
+
+    def update_description(self, number: int, body: str) -> None:
+        self._client.patch_issue_body(number, body)
+
+    def is_org_member(self, org: str, username: str) -> bool:
+        return self._client.is_org_member(org, username)
+
+    def get_pr_for_issue(self, number: int) -> int | None:
+        """Gitea models a PR as an issue with the same number, exposing a
+        `pull_request` object on the issue. When the queried number is
+        itself a PR, return it; otherwise None. (The orchestrator tracks
+        the issue→PR mapping in forge state for the cross-number case.)"""
+        raw = self._client.get_issue(number)
+        if raw.get("pull_request"):
+            return int(raw.get("number", number))
+        return None
+
+    def is_pr_open(self, number: int) -> bool:
+        return self._client.get_pull(number).get("state") == "open"
+
+
+def _read_error_body(exc: urllib.error.HTTPError) -> str:
+    try:
+        return exc.read().decode("utf-8", errors="replace")
+    except Exception:  # pylint: disable=broad-exception-caught
+        return ""