Persistent source code graph for semantic tools

Hi @yogthos,

Dirge already has useful semantic tools based on tree-sitter. Would it make sense to extend them with a persistent source code graph?

The idea is similar to https://github.com/DeusData/codebase-memory-mcp

The graph could store symbols and relations directly from source code, for example:

- functions, classes and files
- calls between functions
- imports and module dependencies
- definitions and references

This could improve:

- callers and callees accuracy
- tracing a path between functions
- impact analysis before changing code
- architecture overview
- incremental indexing after file changes

I saw #393, but I think this is a different graph. #393 stores information from sessions and tool outputs. This proposal is about a graph built directly from the source code.

Later it could also support data flow, Git history relations and cross-repository analysis, but these do not need to be part of the first version.

Do you think this direction fits Dirge?