Add clippy::semicolon_if_nothing_returned workspace lint

[Copilot]

Adds clippy::semicolon_if_nothing_returned = "warn" to the root workspace's [workspace.lints.clippy] and updates all crates — including the code generated by windows-bindgen — to comply.

Changes

Workspace

• Cargo.toml: add the new [workspace.lints.clippy] section.

windows-bindgen generator

• types/enum.rs, types/cpp_enum.rs: emit trailing ; in BitOrAssign/BitAndAssign bodies.
• types/cpp_method.rs:
  • write_upcall ReturnStruct arm: emit trailing ; after the out-pointer write.
  • write_upcall catch-all arm: emit trailing ; when the impl method returns Void (so the void thunk doesn't trigger the lint), otherwise leave the trailing-expression form (HRESULT / value pass-through).
  • write ReturnHint::None arm: emit trailing ; inside the vtable wrapper when the wrapper itself returns unit (avoids the lint on long, multi-line argument lists that rustfmt breaks).

Regenerated content (via cargo run -p tool_bindings and cargo test -p test_bindgen)

• All crates/libs/windows/src/Windows/**/mod.rs files.
• crates/tests/libs/bindgen/data/bindgen/*/expected.rs goldens.

Hand-written fixes in crates the bindgen regen doesn't cover:

• windows-bindgen, windows-metadata, windows-rdl, windows-result, windows-strings.
• Samples: direct3d12, privileges.
• Tests: threading::pool, implement_core::com_object, weak_ref::race, win32::winsock.
• Pre-committed bindings.rs files in crates/tests/misc/component*, crates/samples/windows/webview, and crates/libs/metadata/src/attributes.rs.

Validation

• cargo clippy --workspace --tests --target x86_64-pc-windows-gnu -- -D warnings clean (using the same --exclude windows_*_{msvc,gnu,gnullvm} filter the existing cross-target workflow uses; CI's native cargo clippy --all --tests -- -D warnings on windows-2025 runs the same lint set).
• cargo fmt --all --check clean.
• cargo test -p test_bindgen -p windows-bindgen -p windows-metadata -p windows-rdl passing (324 fixture tests + downstream).
• cargo run -p tool_bindings, tool_workspace, tool_yml produce no further diff.