[cli]: show function debug name in VM fault output (PHX-070-p8)

[JamalLyons]

Summary

• Extend format_vm_error to resolve section 5 function debug names via PcSpanTable::lookup_function_name
• VM fault output now shows {kind} in {name} at {path}:{line}:{col} when names are present; falls back to location-only format for v1 section 5 payloads without names
• Integration tests assert function names appear in nested helper and indirect callee trap stderr

Test plan

• just fmt / just fmt-check
• cargo test -p phx-cli vm_diag
• cargo test -p phx-integration-tests --test sourcemap_run --test sourcemap_multimodule --test release_build
• just pre-commit

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