feat(6242): a repo renamed on its forge keeps its binding and shape ledger

A binding and every row of its project's code-shape ledger are keyed by the
repo's remote. A rename on the forge changes the remote, so binding the new name
started an empty ledger beside the old one and left every judgment behind.

bind_repo now takes moved_from, the old remote. Its binding and the project's
ledger rows move to the new key in one transaction, and the reply says how many
shapes moved. The move is refused when:
- the old name isn't bound to that project;
- the new name is already bound;
- the project already has a ledger under the new name.

Each refusal leaves both names exactly as they were.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/grimoire/mcp/tools/repos.py

@@ -13,7 +13,9 @@ from grimoire.services import projects as projects_svc
 from grimoire.services import repo_bindings as repo_bindings_svc
 
 
-async def bind_repo(repo_url: str, project_id: int, ref: str = "") -> dict:
+async def bind_repo(
+    repo_url: str, project_id: int, ref: str = "", moved_from: str = "",
+) -> dict:
     """Bind a git repository to a Grimoire project for session-start context.
 
     After this, any session started in that repo auto-loads the project's
@@ -27,21 +29,34 @@ async def bind_repo(repo_url: str, project_id: int, ref: str = "") -> dict:
     the push, not the merge. Re-binding with ref="" keeps the standing ref;
     pass ref="-" to clear it back to the default branch.
 
+    A repo renamed on its forge has a new remote, and its ledger is stored
+    under the old one. Pass the old remote as `moved_from` and the binding and
+    every shape judgment move to the new name together. Binding the new name
+    without it starts an empty ledger beside the old one.
+
     Args:
         repo_url: the repo's git remote (e.g. the output of
             `git remote get-url origin` — ssh or https form, both work).
         project_id: the Grimoire project this repo represents.
         ref: branch the ledger follows ("" = leave as is / default branch on
             a new binding; "-" = clear to the default branch).
+        moved_from: the repo's remote before a rename on the forge. The
+            old name must be bound to this project, and the new one must be
+            neither bound nor holding a ledger of this project's.
     """
     uid = current_user_id()
     project = await projects_svc.get_project(uid, project_id)
     if project is None:
         raise ValueError(f"project {project_id} not found")
     ref_arg = None if not ref else ("" if ref.strip() == "-" else ref)
+    moved = None
+    if moved_from:
+        _, moved = await repo_bindings_svc.move_binding(
+            uid, moved_from, repo_url, project_id,
+        )
     binding = await repo_bindings_svc.set_binding(uid, repo_url, project_id, ref_arg)
     follows = binding.ref or "the default branch"
-    return {
+    out = {
         "repo_key": binding.repo_key,
         "project_id": binding.project_id,
         "project_title": project.title,
@@ -51,6 +66,12 @@ async def bind_repo(repo_url: str, project_id: int, ref: str = "") -> dict:
             f"the ledger follows {follows}."
         ),
     }
+    if moved is not None:
+        old_key = repo_bindings_svc.normalize_repo_key(moved_from)
+        out["moved_from"] = old_key
+        out["shapes_moved"] = moved
+        out["message"] += f" Moved from `{old_key}` with {moved} shape(s)."
+    return out
 
 
 async def list_repo_bindings() -> dict: