Function populate_codebase_targeted 

pub fn populate_codebase_targeted(
    codebase: &mut CodebaseMetadata,
    symbol_references: &mut SymbolReferences,
    safe_symbols: WordSet,
    safe_symbol_members: HashSet<SymbolIdentifier>,
    dirty_symbols: HashSet<SymbolIdentifier>,
)

Populates the codebase with an optional set of dirty (invalidated) symbols for targeted iteration.

When dirty_symbols is provided, function-like, class-type, and constant repopulation uses targeted get_mut() lookups instead of scanning the entire HashMap — O(dirty) instead of O(all). This is critical for incremental mode where only a few symbols change per cycle.