fix: ignore explicitly typed variables in misleading_variable_name

[VrtxOmega]

Fixes #1903.

Summary

• skip misleading_variable_name for let bindings with an explicit type annotation
• add a UI regression case proving an explicitly typed binding stays quiet
• document the new fourth condition and regenerate the checked-in example README

Verification

I locally verified the complete amended diff:

• Before the fix, the explicit String binding produced a seventh warning and failed the UI fixture. After the fix, the standalone UI test passes while the six existing warning expectations remain unchanged.
• PATH="$PWD/target/debug:$PATH" CARGO_TARGET_DIR="$PWD/target" cargo +nightly-2026-05-28 test --manifest-path examples/restriction/misleading_variable_name/Cargo.toml — 1 UI test passed
• cargo test -p cargo-dylint --test ci format_example_readmes — 1 README consistency test passed
• cargo +nightly-2026-05-28 fmt --all --check
• git diff --check

Assistance disclosure

OpenAI Codex helped inspect the maintainer feedback and execute the local checks. I reviewed the code change, generated README, diff, and verification output before pushing.

[CLAassistant]

All committers have signed the CLA.

[smoelius]

Thanks, @VrtxOmega. Please forgive me for pasting the below Claude review, but I think I agree with it. Could you please address it?

I think the change should be straightforward, so please fold it into the current commit.

Also, please sign the CLA.

1. The doc comment and generated README are now inaccurate

src/lib.rs:24 still reads:

Checks for variables satisfying the following three conditions:

There are now four. The new condition — the variable has no explicit type annotation — is the one users are most likely to need, since it is the documented way to silence a false positive.

cargo-dylint/tests/ci.rs:343 regenerates every example's README.md from its lint doc comment and asserts equality, so the doc comment and
examples/restriction/misleading_variable_name/README.md must be updated together (BLESS=1 cargo test). CI passes today only because neither file was touched.

Suggested wording:

/// Checks for variables satisfying the following four conditions:
///
/// - The variable is declared without an explicit type.
/// - The variable is initialized with the result of a function call.
/// - The variable's name matches the name of a type defined within the module in which the
///   function is defined.
/// - The variable's type is not the matched type.

[VrtxOmega]

Thanks — addressed in 86edddabe703dc113b10f23d6f24ad5e5cf39769 and folded into the existing commit as requested.

• Updated the rustdoc to describe all four conditions.
• Regenerated the checked-in README through format_example_readmes.
• Signed the Trail of Bits CLA; the CLA check is now passing.
• Re-ran the focused UI test, README consistency test, pinned-nightly format check, and git diff --check; all pass locally.

The amended CI matrix is running now.

[smoelius]

Beautiful. Thank you very much, @VrtxOmega!