tidy: Detect outdated workspaces in workspace list

[clubby789]

Detects the case in #149415 (will pass CI once that lands).

[rustbot]

The list of allowed third-party dependencies may have been modified! You must ensure that any new dependencies have compatible licenses before merging.

cc @davidtwco, @wesleywiser

[rustbot]

r? @Mark-Simulacrum

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[rust-log-analyzer]

The job aarch64-gnu-llvm-20-2 failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)

[TIMING:end] tool::Tidy { compiler: Compiler { stage: 0, host: aarch64-unknown-linux-gnu, forced_compiler: false }, target: aarch64-unknown-linux-gnu } -- 0.000
fmt check
fmt: checked 6575 files
tidy check
tidy [deps]: src/tools/test-float-parse is part of another workspace, remove from `WORKSPACES` (src/tools/tidy/src/deps.rs:114)
tidy [deps]: FAIL
tidy [rustdoc_json (src)]: `rustdoc-json-types` modified, checking format version
tidy: Skipping binary file check, read-only filesystem
tidy: The following check failed: deps
Bootstrap failed while executing `--stage 2 test --skip tests --skip coverage-map --skip coverage-run --skip library --skip tidyselftest`
Command `/checkout/obj/build/aarch64-unknown-linux-gnu/stage1-tools-bin/rust-tidy /checkout /checkout/obj/build/aarch64-unknown-linux-gnu/stage0/bin/cargo /checkout/obj/build 4 yarn` failed with exit code 1
Created at: src/bootstrap/src/core/build_steps/tool.rs:1612:23
Executed at: src/bootstrap/src/core/build_steps/test.rs:1317:29

Command has failed. Rerun with -v to see more details.
Build completed unsuccessfully in 0:00:56
  local time: Fri Nov 28 12:20:38 UTC 2025
  network time: Fri, 28 Nov 2025 12:20:38 GMT
##[error]Process completed with exit code 1.
##[group]Run echo "disk usage:"