chore(sdk): inline direct host wrappers

[lntutor]

Summary

• add bare #[inline] hints to 22 public nx-sdk wrappers that directly trampoline to one host FFI call
• include bounded scalar/result mapping and fixed-size stack-backed hash outputs
• leave dynamic-buffer readers, allocation/parsing paths, loops, private helpers, random_bytes, net, and system::abort unchanged

Verification

• /Users/loi/.cargo/bin/cargo fmt --all --check
• /Users/loi/.cargo/bin/cargo build -p nx-sdk
• /Users/loi/.cargo/bin/cargo test -p nx-sdk
• /Users/loi/.cargo/bin/cargo clippy -p nx-sdk --all-targets -- -D warnings
• /Users/loi/.cargo/bin/cargo test --workspace

Closes #88

[lntutor]

Current head cd695cb2c2efa6ff266df1ad6a1bfcab9a0ff753 is mergeable and the visible CI surface on this exact SHA is fully green: cross-platform Check, Clippy, and Test jobs on Ubuntu, macOS, and Windows; Format; Build WASM Examples; CLI Multi-process Smoke; Benchmark Comparator Tests; Ubuntu Profiling Artifacts; Benchmark Regression Gate; and the aggregate CI Success check all completed successfully. There are no review threads or review-body comments open on the current PR state, so if this direct-host-wrapper cleanup still matches the intended direction, it looks ready for maintainer review/merge when convenient.