Add eagerly-populated methodByOwner index to SymbolTable, keyed by
ownerNodeId\0methodName. Used by walkMixedChain as a fast path for
resolving intermediate method calls in cross-class chains like
user.getAddress().getCity().getZipCode(), avoiding expensive fuzzy
lookups when the owner type is already known.
Handles overloaded methods: returns the first match when all overloads
share the same returnType, undefined when return types differ (ambiguous).
- Add lookupMethodByOwner to SymbolTable interface + implementation
- Add resolveMethodByOwner helper in call-processor.ts
- Add fast path in walkMixedChain before resolveCallTarget fallback
- Add Java cross-class chain fixture + 6 integration tests
- Add 148 unit tests for methodByOwner index behavior
