Use ELF and Mach-O unwind metadata for function boundaries

[haasonsaas]

Context

The extractor uses sized symbols, PE .pdata, and a prologue scan. ELF and Mach-O binaries can contain additional reliable function-start and unwind metadata that is currently discarded.

Proposal

Add format-specific boundary adapters for ELF DWARF/function-start metadata and Mach-O LC_FUNCTION_STARTS/unwind information where available. Each adapter should degrade cleanly when metadata is stripped or malformed.

Acceptance criteria

• Metadata-derived spans are preferred over heuristic spans when valid.
• The source metadata and parser limitations are stored per artifact.
• Fixtures cover present, stripped, truncated, and malformed metadata.
• The extractor never trusts an out-of-range or overlapping span.

References

• format boundary pipeline
• supported formats and limitations