chore: prepare v0.26.2 release

Bump all-smi and all-smi-amd-plugin to 0.26.2 across the workspace manifests, Cargo.lock, the manpage, and Debian changelog, and add the README "Recent Updates" entry.

Cover the 7 merged commits since v0.26.1: Windows hardware doctor corrections (#393), native Windows Clippy and test portability fixes (#394, #395), ordinary Windows CI gates (#396), unavailable Windows GPU metric handling (#400), Level Zero memory provenance correction (#401), and the runtime-loaded Linux AMD companion (#402).

Validated with cargo fmt --all -- --check, cargo check --workspace --all-targets --all-features, cargo clippy --workspace --all-targets -- -D warnings, and cargo test --workspace --all-targets.

The optional Furiosa compile check required BINDGEN_EXTRA_CLANG_ARGS for the installed GCC header path because this host has no Clang executable. All-feature tests could not link because libfuriosa_smi is not installed, and all-feature Clippy reports five warnings in unchanged Furiosa reader code under Rust 1.97 and 1.98.