The rename impl narrows on SessionTitleInvalidError: only an
empty-normalizing title maps to title-invalid (its message renders verbatim
in the rename dialog alert), while liveness/disposal races fall to internal;
the absent-service message trims to one presentable sentence. rpc-schemas
gains the title-invalid accept/missing-details lines; cosmetic ordering
(type-only import comment, tsconfig reference, schema import order) restored.