Function discover_savecontext_dir 

pub fn discover_savecontext_dir() -> Option<PathBuf>

Discover the SaveContext directory (legacy behavior).

Walks up from the current directory looking for .savecontext/, falling back to the global location.

Note: For new code, prefer:

• resolve_db_path() for database access (uses global DB)
• discover_project_savecontext_dir() for export directory (per-project)

Returns

Returns the path to the .savecontext/ directory, or None if not found.