feat(file): make Footer::new public

[tobias-fire]

Rationale for this change

vortex-file already exposes everything needed to write a Vortex file without the bundled VortexWriteOptions::write driver — the SegmentSink trait, accumulate_stats, FileStatistics, FooterSerializer, etc. are all public — except the final step of constructing the Footer. Footer::new is pub(crate), so downstream code that drives the layout/segment-write pipeline directly (e.g. a custom LayoutStrategy paired with a custom SegmentSink) has to either fork the crate or re-implement the writer inside it just to assemble the footer. This closes that single gap.

What changes are included in this PR?

• Change Footer::new from pub(crate) to pub.

No behavioral change and no new dependencies. cargo check and cargo fmt --check pass locally.

What APIs are changed? Are there any user-facing changes?

One additive, non-breaking change: vortex_file::Footer::new is now public. Nothing else changes.

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AI assistance disclosure: prepared with an agentic AI coding assistant (Claude Code), per the project's AI policy. The author reviewed the change and verification steps.

[codspeed-hq]

Merging this PR will improve performance by 12.06%

⚠️ Unknown Walltime execution environment detected

Using the Walltime instrument on standard Hosted Runners will lead to inconsistent data.

For the most accurate results, we recommend using CodSpeed Macro Runners: bare-metal machines fine-tuned for performance measurement consistency.

⚠️ 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

⚡ 2 improved benchmarks
✅ 1587 untouched benchmarks
⏩ 4 skipped benchmarks¹

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
⚡	Simulation	bitwise_not_vortex_buffer_mut[128]	244.4 ns	215.3 ns	+13.55%
⚡	Simulation	bitwise_not_vortex_buffer_mut[1024]	304.7 ns	275.6 ns	+10.58%

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 tobias-fire:th/public-file-footer-new (febc53b) with develop (9567467)}

Footnotes

1. 4 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. ↩