fix: Wire graph packer to depthFilter — real content instead of stubs

[VictorGjn]

Problem

contentAtDepth() in src/graph/packer.ts generates descriptive stubs instead of calling depthFilter.ts for real filtered content. The bridge is not wired. The depth system's core value (3-5x more context in same token budget) doesn't actually work in the graph pipeline.

Additionally, calls detection in extractors/code.ts matches too aggressively: any identifier + ( matches against every export.

Success criteria

• contentAtDepth() calls depthFilter.ts and returns real depth-filtered content
• COMMON_IDENTIFIERS blocklist extended
• Scope filter reduces false positive calls edges by 5x

Implementation

1. src/graph/packer.ts → import depthFilter, replace contentAtDepth() stub
2. src/graph/extractors/code.ts → add scope filter (same-file = ignore)
3. Extend COMMON_IDENTIFIERS
4. Test: scan modular-patchbay, verify calls edges < 200