feat: fold bot-bottle-orchestrator into bot_bottle/orchestrator subpackage

Moves the orchestrator into bot_bottle/orchestrator/ so one install gets
everything. Entry point is now `python -m bot_bottle.orchestrator run`.

- Add bot_bottle/orchestrator/ with all 14 modules (verbatim move; internal
  imports were already relative, so no changes inside orchestrator modules)
- Rewrite bootstrap.py: remove the lazy bot_bottle import guard, use direct
  relative imports from ..contrib.*
- Add bot_bottle/contrib/forge/base.py: ScopedForge (read-anywhere / write-scoped)
- Add bot_bottle/contrib/gitea/client.py: GiteaClient + GiteaForge (urllib.request only)
- Add bot_bottle/contrib/gitea/forge_state.py: ForgeState + SqliteForgeStateStore
- Add tests/unit/orchestrator/ (82 tests: 63 migrated + 19 new for contrib modules)

Closes #321

bot_bottle/contrib/gitea/client.py

@@ -0,0 +1,112 @@
+"""Gitea API client and forge adapter (PRD prd-new: fold orchestrator).
+
+`GiteaClient` is a thin HTTP wrapper (stdlib `urllib.request` only — no
+new runtime dependencies). `GiteaForge` composes a client and exposes
+the forge protocol used by the orchestrator's sidecar and lifecycle.
+
+Required Gitea token scopes:
+- Repository: Read & Write (issues, comments, PR descriptions)
+- Organization: Read (org membership check)
+"""
+
+from __future__ import annotations
+
+import json
+import urllib.error
+import urllib.request
+from typing import Any
+
+_TIMEOUT_SECS = 30
+
+
+class GiteaClient:
+    """Low-level HTTP wrapper for the Gitea REST API."""
+
+    def __init__(
+        self, *, api_url: str, owner: str, repo: str, token: str
+    ) -> None:
+        self._base = api_url.rstrip("/")
+        self._owner = owner
+        self._repo = repo
+        self._headers = {
+            "Authorization": f"token {token}",
+            "Content-Type": "application/json",
+            "Accept": "application/json",
+        }
+
+    def _request(
+        self,
+        method: str,
+        path: str,
+        body: dict[str, Any] | None = None,
+    ) -> Any:
+        url = f"{self._base}{path}"
+        data = json.dumps(body).encode() if body is not None else None
+        req = urllib.request.Request(
+            url, data=data, headers=self._headers, method=method
+        )
+        with urllib.request.urlopen(req, timeout=_TIMEOUT_SECS) as resp:
+            raw = resp.read()
+            return json.loads(raw) if raw else None
+
+    def is_org_member(self, org: str, username: str) -> bool:
+        url = f"{self._base}/orgs/{org}/members/{username}"
+        req = urllib.request.Request(url, headers=self._headers, method="GET")
+        try:
+            urllib.request.urlopen(req, timeout=_TIMEOUT_SECS).close()
+            return True
+        except urllib.error.HTTPError:
+            return False
+
+    def get_issue(self, number: int) -> dict[str, Any]:
+        return self._request("GET", f"/repos/{self._owner}/{self._repo}/issues/{number}")
+
+    def get_pull(self, number: int) -> dict[str, Any]:
+        return self._request("GET", f"/repos/{self._owner}/{self._repo}/pulls/{number}")
+
+    def list_comments(self, number: int) -> list[dict[str, Any]]:
+        return self._request("GET", f"/repos/{self._owner}/{self._repo}/issues/{number}/comments")
+
+    def create_comment(self, number: int, body: str) -> None:
+        self._request(
+            "POST",
+            f"/repos/{self._owner}/{self._repo}/issues/{number}/comments",
+            {"body": body},
+        )
+
+    def update_issue(self, number: int, body: str) -> None:
+        self._request(
+            "PATCH",
+            f"/repos/{self._owner}/{self._repo}/issues/{number}",
+            {"body": body},
+        )
+
+
+class GiteaForge:
+    """Adapts `GiteaClient` to the forge protocol expected by the orchestrator.
+
+    The forge protocol is duck-typed: any object with `is_org_member`,
+    `read_issue`, `read_pr`, `read_comments`, `post_comment`, and
+    `update_description` methods satisfies it.
+    """
+
+    def __init__(self, client: GiteaClient) -> None:
+        self._client = client
+
+    def is_org_member(self, org: str, username: str) -> bool:
+        return self._client.is_org_member(org, username)
+
+    def read_issue(self, number: int) -> dict[str, Any]:
+        return self._client.get_issue(number)
+
+    def read_pr(self, number: int) -> dict[str, Any]:
+        return self._client.get_pull(number)
+
+    def read_comments(self, number: int) -> list[dict[str, Any]]:
+        return self._client.list_comments(number)
+
+    def post_comment(self, number: int, body: str) -> None:
+        self._client.create_comment(number, body)
+
+    def update_description(self, number: int, body: str) -> None:
+        self._client.update_issue(number, body)