v0.4.18 -- cross-file call resolution + semantic/AST ID fix

• Cross-file call resolution for Go, Rust, Zig, PowerShell, and Elixir (raw_calls saved and resolved globally)
• Fix semantic/AST node ID mismatch: build.py now reconciles mismatched IDs so LLM-generated edges survive the merge
• skill.md: explicit node ID generation rules with example to reduce LLM ID drift