Everything the call-graph builder reads, sourced from the GraphProvider
facade (PropertyGraph). Replaces the former direct ProjectIndex
dependency (#696): the file inventory, the symbol table (for enclosing-symbol
attribution) and the import/reexport adjacency (for scope-aware callee
resolution). Source content itself is still read fresh from disk per file.
Resolve callee names to a single defining file when scope makes it
unambiguous across all call sites. Names that resolve to different files
from different scopes are omitted, so callers never attribute a call to the
wrong file. Keyed by callee name to match the call graph’s name-keyed nodes.