fix: restrict wasm-bindgen to browser wasm, fixing wasip1 builds

[0ax1]

wasm-bindgen 0.2.115 changed its cfg guard from
cfg(all(target_arch = "wasm32", target_os = "unknown")) to cfg(target_family = "wasm"), causing __wbindgen_* imports to be emitted for all wasm targets including wasm32-wasip1. Combined with wasm-test/Cargo.lock being untracked (deleted in #6187), CI picked up the new version and the wasmer integration test broke.

Narrow the wasm-bindgen-futures dependency and the wasm runtime module in vortex-io from cfg(target_arch = "wasm32") to cfg(all(target_arch = "wasm32", target_os = "unknown")), which matches only wasm32-unknown-unknown (browser) and excludes WASI targets. For the fuzz crate's wasip1 target, provide a session without an async runtime handle since the fuzz workloads are synchronous.

[AdamGS]

🚢

[codspeed-hq]

Merging this PR will degrade performance by 15.51%

❌ 2 regressed benchmarks
✅ 1104 untouched benchmarks
⏩ 1522 skipped benchmarks¹

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
❌	Simulation	bitwise_not_vortex_buffer_mut[128]	317.8 ns	376.1 ns	-15.51%
❌	Simulation	bitwise_not_vortex_buffer_mut[1024]	477.2 ns	535.6 ns	-10.89%

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_{Comparing ad/fix-wasi-build (175de98) with develop (2258dd3)}

Footnotes

1. 1522 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. ↩