Add probe-queue-contention, which prices the tail claim

.github/copilot-instructions.md

@@ -492,8 +492,7 @@ the same time, so both halves of the evidence disappear together.
 This is not a small correction. Measured on two runs here: a `windows-topology-sys` sweep
 reported 61 survivors of which **57 were in `#[cfg(feature = "serde")]` code**, and a
 `windows-file-watcher` sweep reported 247 of which **147 were in `scenario-tool` and
-`test-util` modules**. In both cases roughly 60% of the "gaps" were artifacts of the
-invocation. So:
+`test-util` modules**. In both cases the gated code dominated the survivor list. So:
 
 ```
 cargo mutants -p <crate> --all-features
@@ -1271,6 +1270,103 @@ Two corollaries that have each already cost a review round:
   written while the old reading was current — generators, test doubles, examples — because those
   encode the reading rather than citing it.
 
+### 4. Prose carries the claim; a number belongs in an artifact
+
+Measured data pasted into prose becomes a copy somebody must keep true by hand, in every place it
+was pasted, forever. Markdown has no include and rustdoc has no data include, so pasting is the path
+of least resistance — and it is where this repository's documentation defects overwhelmingly come
+from. Measured on one pull request's review history: almost none of its measurement findings were
+*wrong measurements*; they were transcriptions that drifted — a table disagreeing with its own copy
+one file away, an attribution naming a superseded capture, one horizon left unqualified across seven
+sites in three wordings.
+
+- **Write the claim, not the digits, wherever the digits are not the point.** "Measured faster under
+  contention, and the spread is wide enough that the ordering is a flag rather than a finding" cannot
+  drift from the data, because it restates none of it.
+- **When a figure must appear, it has exactly one home.** Prefer a committed capture the prose links
+  to (`mutation-sweeps/<date>/` is this repository's existing example) over the same figure typed
+  into two documents. Provenance — host, commit, date — travels with the data rather than in a
+  hand-maintained table beside it.
+- **Never restate a proportion over data you already showed.** A ratio over counts in the same
+  document is not a finding; it is a hand-computed copy of one, checked by nobody and stale the
+  moment any input moves. The counts are the finding. This rule was earned: an instructions file in
+  this repository claimed "in both cases roughly 60%" about two figures given four words earlier,
+  one of which was 57 of 61 — 93%.
+- **The same applies to incidental tallies** — test counts, file counts, line counts. If the number
+  is not itself the finding, leave it out; "the gate is green" says what "308 lib tests" pretends to.
+
+**This is the data-side twin of rule 1.** Rule 1 says define a fact once in code and have everything
+ask. This says the same of measurements: hold the number once, and have prose point rather than
+paraphrase.
+
+## REVIEW FEEDBACK — answer it where it was raised, not only in the commit
+
+**A review round is not finished when the code changes. It is finished when the reviewer has
+been told what happened.** Fixing the code and pushing is half the transaction; the other half
+is a reply on GitHub, and omitting it is the default failure mode because the fix *feels* like
+completion. It is not, for three reasons:
+
+- **A commit is not an answer.** The reviewer sees a new SHA, not your reasoning. Nothing
+  connects "I changed `format_ratio`" to the finding that asked for it, so the next round
+  re-raises what was already addressed — which has repeatedly cost rounds on this repository.
+- **Some findings are correctly declined, and silence cannot say so.** A declined finding that
+  is never answered is indistinguishable from one that was missed. Declining is legitimate;
+  declining *silently* is not.
+- **Suppressed comments have no thread at all.** They arrive in the review summary rather than
+  attached to a line, so there is no place a reply can land by default and no automatic record
+  that they were read. They are the easiest feedback to drop and the most likely to be re-raised
+  verbatim in the next round.
+
+### What to do, by where the feedback lives
+
+- **Inline review comments (a thread on a line).** Reply *on that thread*, naming what changed
+  and the commit SHA that changed it. Then resolve the thread — but only if the finding is
+  genuinely discharged; never resolve to clear the queue. Use the `resolveReviewThread` tool, or
+  `gh api repos/{owner}/{repo}/pulls/{number}/comments/{comment_id}/replies -f body=...`.
+- **Suppressed comments, review-summary findings, and anything pasted to you out of band** — no
+  thread exists, so post **one new PR comment** covering that round:
+  `gh pr comment <number> --body-file .scratch/<file>.md`. One comment per round, not one per
+  finding; a reviewer reads the round as a unit.
+- **No PR** (work committed straight to a branch, or feedback on a commit):
+  `gh api repos/{owner}/{repo}/commits/{sha}/comments -f body=...` against the commit that
+  carries the response.
+
+### What the response must contain
+
+Every finding in the round gets a line, and each line is one of exactly two things:
+
+1. **Changed** — what was changed and the SHA. Where the fix was a *sweep* rather than a
+   single-line edit (per CONTRACT INTEGRITY rule 3 above), say so and give the count: "swept
+   `QueueFull`: 13 files, 4 updated". A reviewer who sees only the cited line fixed has no way
+   to know the population was covered.
+2. **Declined** — the argument for why, in enough detail to be argued back against. "Not
+   applicable" is not an argument; "this is gated behind `test-util`, so the mutant sits in code
+   the shipping build never compiles" is.
+
+Two further rules, each of which has already cost a round here:
+
+- **Do not claim a fix you have not verified.** The same standard applies as anywhere else in
+  this file: verify by execution. Where the fix was a test, say what sabotage showed it is
+  load-bearing — an unverified "added a test" is exactly the cosmetic binding CONTRACT INTEGRITY
+  rule 1 warns about.
+- **Report what the round taught, not just what it touched.** When a review round reveals that
+  several findings were one underlying error, say that — it is more useful to the reviewer than
+  five separate acknowledgements, and it is how a recurring defect gets named instead of
+  repeatedly re-fixed.
+
+### The PR description drifts too, and nothing greps it
+
+A PR body is prose that restates measured claims, gate results, and design rationale — so it
+rots exactly like the documents CONTRACT INTEGRITY governs, with one difference: **it is not a
+file in the tree, so no sweep, grep, or CI check will ever catch it.** When a round corrects a
+claim, check whether the PR description states the same claim, and correct it in the same round.
+
+Keep out of the PR body anything that drifts without carrying information. **Test counts are the
+standing example**: "308 lib tests" changes on almost every commit, tells a reader nothing that
+"tests pass" does not, and creates a restatement-drift instance out of nothing. State that the
+gate is green and which parts of it ran; do not enumerate. The same goes for file counts, line
+counts, and any other incidental tally that is not itself the finding.
+
 ## CHECKLIST file hygiene
 
 CHECKLIST files are **action-only**: they contain pending, in-progress, and recently

.github/workflows/ci.yml

@@ -500,6 +500,45 @@ jobs:
           RUSTDOCFLAGS: "-D rustdoc::broken_intra_doc_links -D rustdoc::private_intra_doc_links"
         run: cargo doc -p windows-placement-probe --no-deps --no-default-features --locked
 
+  waitable-queues-default-features:
+    name: windows-waitable-queues (default features)
+    runs-on: windows-latest
+    # **This job exists because adding `probe-queue-contention` took the default
+    # configuration away from every other job.** That probe needs `dwcas` and
+    # `experimental-permit-claim`, and enabling them on a workspace member
+    # unifies them across the whole workspace -- so the `--workspace` steps that
+    # deliberately omit `--all-features` stopped being a default-features build
+    # of THIS crate, and no job was left compiling it without `dwcas`.
+    #
+    # That matters because `dwcas` is additive: `Wide` and its `ClaimLayout` impl
+    # exist only under it, so the configuration that loses them is the one that
+    # can break unnoticed. The crate's manifest says `dwcas` is "non-default so
+    # nothing depends on it by accident" and is "the only thing in this crate
+    # that costs a third-party dependency" -- a claim that is only true while
+    # something still builds without it.
+    #
+    # Named per-crate rather than fixed by making the probe's dependency
+    # optional: the probe must stay buildable by a plain `cargo build`, and a
+    # feature that has to be remembered before the probe compiles is a worse
+    # trade than a job that cannot be forgotten.
+    env:
+      RUSTUP_TOOLCHAIN: stable
+    steps:
+      - uses: actions/checkout@v7
+      - uses: dtolnay/rust-toolchain@stable
+        with:
+          components: clippy
+      - uses: Swatinem/rust-cache@v2
+      - name: cargo build
+        run: cargo build -p windows-waitable-queues --all-targets --locked
+      - name: cargo clippy
+        run: cargo clippy -p windows-waitable-queues --all-targets --locked -- -D warnings
+      - name: cargo test
+        env:
+          RUST_BACKTRACE: 1
+          RUST_LIB_BACKTRACE: 1
+        run: cargo test -p windows-waitable-queues --locked --no-fail-fast
+
   fmt:
     name: rustfmt
     runs-on: windows-latest