Search history displays invalid results after switching graphs

[Naseem77]

Title: search history displays invalid results after switching graphs

Description:
When switching to a different graph, the previously saved search history remains accessible, even though the paths are no longer valid for the newly selected graph. Clicking on these invalid history entries incorrectly attempts to show a path, but instead focuses on a random node or shows no path at all

Steps to Reproduce:

1. Navigate to code graph home page
2. Select a graph from the dropdown menu.
3. Perform a "Show Path" action between two nodes
4. Repeat step 3 with different paths to generate multiple entries in the chat history.
5. Switch to a different graph using the dropdown menu.
6. Click on one of the previously saved path entries in the chat history.

Expected Behavior:

Upon switching to a new graph, saved search history entries that are no longer valid should either:

• Be disabled with a message explaining their irrelevance.
• Be removed entirely.
• Prompt the user with a message indicating the path is invalid for the current graph.