fix: credit Next.js metadata route config exports

[BartWaardenburg]

Summary

• Credit the six framework-consumed segment config exports on Next.js App Router metadata route files, while keeping dynamicParams and arbitrary helpers reportable.
• Correct the remaining Knip migration suggestion to use unresolved-import and validate its semantic mapping.
• Clarify that --save-regression-baseline without a path updates the discovered config, with an end-to-end CLI regression test.
• Confirm the existing -- suppression reason terminator preserves the reason without parsing its words as issue kinds.

Verification

• targeted red-green unit and integration regressions
• cargo test --workspace --lib --bins --tests
• cargo check --workspace
• cargo clippy --workspace --all-targets -- -D warnings
• cargo fmt --all -- --check
• cargo doc --workspace --no-deps --document-private-items
• release build
• Acorn real-project comparison against fallow 2.86.0
• suppression reason CLI reproduction against fallow 2.86.0
• ecosystem end-to-end suite
• fallow audit --format json --quiet

[codspeed-hq]

Merging this PR will improve performance by ×5.6

⚠️ Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

⚡ 1 improved benchmark
✅ 45 untouched benchmarks
⏩ 32 skipped benchmarks¹

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
⚡	reverse_re_export_chain[64]	5,483.3 µs	972.8 µs	×5.6

Tip

Curious why this is faster? Comment @codspeedbot explain why this is faster on this PR, or directly use the CodSpeed MCP with your agent.

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_{Comparing fix/next-metadata-route-config-hints (0020d14) with main (811fa40)}

Footnotes

1. 32 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩