fix: guard remote/repo mismatch vs local git remote (Closes #530)

Bare remote=prgs resolved to the hardcoded REMOTES default
Scaled-Tech-Consulting/Timesheet instead of the Gitea-Tools repository
the local git remote points at, causing false 404s and risking mutation
of a different repository.

Add remote_repo_guard.assess_remote_repo_match (pure) + formatter, wired
into gitea_mcp_server._resolve so every read/lookup/mutation tool fails
closed when the MCP-resolved org/repo disagrees with the local git remote
URL and the caller did not pass explicit org/repo. The guard is
best-effort: it skips when both org and repo are explicit, when the local
remote URL is unavailable, and is bypassed under pytest unless
GITEA_FORCE_REMOTE_REPO_CHECK is set.

Add tests/test_remote_repo_guard.py (pure-function cases + server wiring
proving a lookup tool cannot silently query a different repository), and
update author/reviewer/merger handoff templates to require explicit
remote/org/repo.

Closes #530

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

remote_repo_guard.py

@@ -0,0 +1,98 @@
+"""Remote/repo mismatch guard (#530).
+
+Bare ``remote`` names resolve to a default ``org``/``repo`` via the ``REMOTES``
+table in :mod:`gitea_auth`. For the ``prgs`` instance the hardcoded default repo
+is ``Timesheet``, but the tools in this project operate on
+``Scaled-Tech-Consulting/Gitea-Tools``. When a session runs inside a Gitea-Tools
+worktree and calls a tool with a bare ``remote=prgs`` (no explicit ``org``/``repo``),
+the resolved target silently points at the wrong repository, producing false 404s
+and risking mutation of a different repo.
+
+This module provides a pure assessment that compares the MCP-resolved ``org/repo``
+against the local git remote URL and fails closed on a genuine mismatch, unless the
+caller supplied explicit ``org``/``repo`` (in which case their intent is authoritative)
+or the local remote URL is unavailable (best-effort corroboration only).
+"""
+
+from __future__ import annotations
+
+REMEDIATION = (
+    "Pass explicit org= and repo= matching the local git remote, "
+    "e.g. org=Scaled-Tech-Consulting repo=Gitea-Tools."
+)
+
+
+def assess_remote_repo_match(
+    *,
+    remote: str,
+    resolved_org: str,
+    resolved_repo: str,
+    local_remote_url: str | None,
+    org_explicit: bool,
+    repo_explicit: bool,
+) -> dict:
+    """Fail closed when the resolved org/repo disagrees with the local git remote.
+
+    The guard is intentionally conservative:
+
+    * When the caller passed both ``org`` and ``repo`` explicitly, their intent is
+      authoritative and the guard never blocks.
+    * When the local git remote URL is unavailable (``None``/empty), corroboration
+      is impossible, so the guard does not block (best-effort only).
+    * Otherwise, the resolved ``org/repo`` slug must appear in the local remote URL
+      (case-insensitive); if it does not, the guard blocks.
+    """
+    reasons: list[str] = []
+
+    if org_explicit and repo_explicit:
+        return _assessment(True, reasons, remote, resolved_org, resolved_repo, local_remote_url)
+
+    url = (local_remote_url or "").strip()
+    if not url:
+        return _assessment(True, reasons, remote, resolved_org, resolved_repo, local_remote_url)
+
+    expected_slug = f"{resolved_org}/{resolved_repo}".lower()
+    if expected_slug in url.lower():
+        return _assessment(True, reasons, remote, resolved_org, resolved_repo, local_remote_url)
+
+    reasons.append(
+        f"MCP-resolved repository '{resolved_org}/{resolved_repo}' for remote "
+        f"'{remote}' does not match the local git remote URL '{url}'"
+    )
+    return _assessment(False, reasons, remote, resolved_org, resolved_repo, local_remote_url)
+
+
+def format_remote_repo_guard_error(assessment: dict) -> str:
+    """Single RuntimeError message for the MCP resolver gate."""
+    reasons = "; ".join(
+        assessment.get("reasons") or ["remote/repo resolution mismatch"]
+    )
+    resolved = (
+        f"{assessment.get('resolved_org')}/{assessment.get('resolved_repo')}"
+    )
+    local = assessment.get("local_remote_url") or "(unknown)"
+    return (
+        f"Remote/repo guard (#530): {reasons}. "
+        f"Resolved target: {resolved}; local git remote: {local}. "
+        f"{REMEDIATION}"
+    )
+
+
+def _assessment(
+    proven: bool,
+    reasons: list[str],
+    remote: str,
+    resolved_org: str,
+    resolved_repo: str,
+    local_remote_url: str | None,
+) -> dict:
+    return {
+        "proven": proven,
+        "block": not proven,
+        "reasons": reasons,
+        "remote": remote,
+        "resolved_org": resolved_org,
+        "resolved_repo": resolved_repo,
+        "local_remote_url": local_remote_url,
+        "remediation": REMEDIATION,
+    }