[oddharsh]

Add srgb_lut16() and g22_lut16() so Rust callers can decode unsigned 16-bit samples to linear f32 without an 8-bit intermediate or a power function per sample. This moves the tested implementation from site #854 into the crate that already owns resampling and 8-bit transfer functions.

Each curve lazily allocates a 256 KiB table directly on the heap. Both bit depths share the normalized curve implementation; existing public APIs and the JavaScript surface retain their behavior. No dependencies or MSRV changes.

Validation:

• Exhaustive bit equality for all 65,536 values under both curves, against the original site formulas, in debug and release builds.
• The integration test initializes both tables on a cold 128 KiB thread stack, guarding against the temporary-array stack overflow found during the site experiment.
• Existing 8-bit tests, both doctests, five conformance tests, workspace Clippy and formatting pass.
• Rust 1.75 check passes. WebAssembly build and all three JavaScript tests pass; wasm is 13,613 bytes gzip, below the 40,000-byte gate.
• Site #854 now consumes this exact commit. Comparing its previous binary with the new dependency produced identical bytes for all 312 outputs across 52 full-resolution originals (46 JPEGs and six HIFs): 208 thumbnail tier files, 52 width-capped PNGs and 52 q84 JPEG encodes. All 258 site histograms also match. The site's 38 Rust tests, including exhaustive checks through its four 16-bit loader formats, pass in the consumer build.

Local wasm-pack printed prebuilt-binary/update and package-metadata notices; the build completed successfully using the available tooling.