bf72282f8e
merge_bottles_runtime used .get(n, base_repos_by_name[n]) which eagerly evaluates the default, crashing when a repo exists only in the override bottle. Replaced with a conditional expression so the base lookup only runs when needed. Adds three regression tests covering override-only, base-only, and name-collision cases. Closes #457 Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>