chore: fix all clippy issues and strengthen CI lint coverage

[karthiknadig]

Problem

cargo clippy --workspace --all-targets --all-features -- -D warnings fails on test code that the CI lint job never checks, because lint.yml runs cargo clippy --all-features without --all-targets and only on Linux. Issues found:

• crates/pet-hatch/src/lib.rs (x4) — needless_borrows_for_generic_args (norm_case(&path.join(...)))
• crates/pet/tests/jsonrpc_server_test.rs:70 — needless_return
• crates/pet/tests/e2e_performance.rs:764 — expect_fun_call (.expect(&format!(...)))

These never failed CI because the lint job skips test targets.

Fix

• Fix all of the above clippy findings.
• Strengthen the CI lint job (lint.yml) to run cargo clippy --workspace --all-targets --all-features -- -D warnings so test code and feature-gated code are linted.
• Run clippy on both Linux and Windows runners so platform-gated code is covered.

Context

Discovered while fixing #432.