chore(cargo): declare MSRV and release metadata

[lemtoc]

Issue

Fixes #30

Changes

• Declare Rust 1.88 as the MSRV and add crates.io package metadata.
• Keep release and dist builds on panic unwinding, with manifest tests guarding worker job isolation.
• Add an MSRV CI job that checks all locked targets on Rust 1.88.0.

Verification

• Cargo metadata exposes the declared MSRV, README, keywords, and category.
• Release and dist profiles retain panic unwinding required by catch_unwind.

Additional Notes

• Rust 1.88 is the actual minimum because Nova uses edition 2024 let chains stabilized in that release.
• Local zsh-bench (16 runs): first prompt 29.0 ms, command lag 0.487 ms, input lag 0.596 ms.
• Interactive zsh verification is not required because shell initialization and rendering behavior are unchanged.

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[github-actions]

Nova zsh-bench

metric	median	previous	delta	status	green	yellow	orange	red
first prompt lag	37.81 ms	30 ms	+7.81 ms	yellow	25 ms	50 ms	100 ms	> 100 ms
first command lag	38.19 ms	30.14 ms	+8.05 ms	green	75 ms	150 ms	300 ms	> 300 ms
command lag	1.15 ms	0.59 ms	+0.56 ms	green	5 ms	10 ms	20 ms	> 20 ms
input lag	0.73 ms	0.43 ms	+0.3 ms	green	10 ms	20 ms	40 ms	> 40 ms

Previous is the stored benchmark for 8766502.
Delta is current median minus previous median. Lower is faster.

Red status fails CI. Values are medians from zsh-bench raw iterations.

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