chore(rust/clippy): enable allow_attributes

Convert every #[allow] in the workspace to #[expect]. The conversion
immediately paid for itself by surfacing four suppressions whose lint
no longer fires:

- resolve_peers: a too_many_arguments expect on a three-argument
  method (stale since a refactor) - removed.
- resolve_peers: two dead_code expects on MissingPeerInfo fields the
  compiler considers used - removed.
- tarball: fetch_and_extract_zip_once stacked two copies of the same
  too_many_arguments suppression - deduplicated.
- ensure_file: a cfg_attr(windows, allow(unused)) on a mode parameter
  that IS used on Windows (via verify_or_rewrite) - removed.

The remaining windows-side cfg_attr suppressions become expect with a
reason, and fire correctly there (the parameters are genuinely unused
on that cfg).

Cargo.toml

@@ -256,6 +256,11 @@ pathbuf_init_then_push = "warn"
 string_add             = "warn"
 verbose_file_reads     = "warn"
 
+# attribute hygiene (restriction): #[expect] over #[allow], so a suppression
+# whose lint stops firing surfaces as an unfulfilled-expectation warning
+# instead of silently going stale.
+allow_attributes = "warn"
+
 [profile.release]
 opt-level     = 3
 lto           = "fat"

pacquet/crates/fs/src/ensure_file.rs

@@ -166,7 +166,7 @@ pub fn ensure_parent_dir(dir: &Path) -> Result<(), EnsureFileError> {
 pub fn ensure_file(
     file_path: &Path,
     content: &[u8],
-    #[cfg_attr(windows, allow(unused))] mode: Option<u32>,
+    mode: Option<u32>,
 ) -> Result<(), EnsureFileError> {
     // See the "Process-local per-path mutex" bullet above and
     // [`cas_write_lock`] for the rationale.
@@ -375,7 +375,8 @@ fn file_equals_bytes(file_path: &Path, content: &[u8]) -> io::Result<bool> {
 fn write_atomic(
     file_path: &Path,
     content: &[u8],
-    #[cfg_attr(windows, allow(unused))] mode: Option<u32>,
+    #[cfg_attr(windows, expect(unused, reason = "mode is only applied on POSIX platforms"))]
+    mode: Option<u32>,
 ) -> Result<(), EnsureFileError> {
     /// Retries after `AlreadyExists` on the temp path. Sixteen fresh
     /// counter values is plenty — under benign conditions we never
@@ -515,7 +516,10 @@ fn rename_with_retry(src: &Path, dst: &Path) -> io::Result<()> {
 /// classifier is disabled and any `rename` error propagates
 /// immediately.
 fn is_transient_rename_error(
-    #[cfg_attr(not(windows), allow(unused, reason = "only inspected in the Windows branch below"))]
+    #[cfg_attr(
+        not(windows),
+        expect(unused, reason = "only inspected in the Windows branch below")
+    )]
     error: &io::Error,
 ) -> bool {
     #[cfg(windows)]

pacquet/crates/fs/src/ensure_file/tests.rs

@@ -73,7 +73,7 @@ fn missing_parent_dir_errors() {
 }
 
 /// Unix mode is honoured on the new-file path. Skipped on Windows
-/// where the `mode` argument is `#[cfg_attr(windows, allow(unused))]`.
+/// where the `mode` argument is only applied on POSIX platforms.
 ///
 /// Asserts the **owner** bits specifically rather than the full
 /// `0o777` triplet because `OpenOptionsExt::mode` runs through the

pacquet/crates/fs/src/file_mode.rs

@@ -19,7 +19,7 @@ pub fn is_executable(mode: u32) -> bool {
 
 /// Set file mode to 777 on POSIX platforms such as Linux or macOS,
 /// or do nothing on Windows.
-#[cfg_attr(windows, allow(unused))]
+#[cfg_attr(windows, expect(unused, reason = "the file param is only touched on POSIX platforms"))]
 pub fn make_file_executable(file: &std::fs::File) -> io::Result<()> {
     #[cfg(unix)]
     return {

pacquet/crates/package-manager/src/build_modules.rs

@@ -605,7 +605,7 @@ impl BuildModules<'_> {
 /// dispatch can call it once per chunk member. The body is the same
 /// as the pre-`#12` sequential loop — `continue`s become `return Ok(())`
 /// here.
-#[allow(
+#[expect(
     clippy::too_many_arguments,
     reason = "the parameters are independent inputs; bundling them into a struct would not improve clarity"
 )]

pacquet/crates/package-manager/src/symlink_direct_dependencies.rs

@@ -373,7 +373,7 @@ pub(crate) fn importer_root_dir(workspace_root: &Path, importer_id: &str) -> Pat
     }
 }
 
-#[allow(
+#[expect(
     clippy::too_many_arguments,
     reason = "the parameters are independent inputs; bundling them into a struct would not improve clarity"
 )]

pacquet/crates/resolving-deps-resolver/src/resolve_peers.rs

@@ -559,9 +559,7 @@ struct NodeRecord {
 /// directly, so neither field is read after construction yet.
 #[derive(Debug, Clone)]
 struct MissingPeerInfo {
-    #[allow(dead_code, reason = "future peersCache validation")]
     range: String,
-    #[allow(dead_code, reason = "future peersCache validation")]
     optional: bool,
     /// See [`crate::dependencies_graph::MissingPeer::meta_only`].
     meta_only: bool,
@@ -1129,10 +1127,6 @@ impl Walker<'_> {
         }
     }
 
-    #[allow(
-        clippy::too_many_arguments,
-        reason = "splitting these into a struct would only obscure the call site"
-    )]
     /// `true` when a missing-peer issue for `peer_name` under the
     /// given ancestor chain must not be emitted for the hoist input.
     /// See [`ResolvePeersOptions::hoist_missing_scope`].

pacquet/crates/resolving-npm-resolver/src/pick_package.rs

@@ -681,7 +681,7 @@ pub async fn pick_package<Cache: PackageMetaCache>(
 /// Bundling these into a struct would just shuffle the same fields
 /// into a wrapper without removing any work; allowing the lint is
 /// the lower-noise option.
-#[allow(
+#[expect(
     clippy::too_many_arguments,
     reason = "bundling these independent inputs into a struct moves the fields into a wrapper without removing work"
 )]

pacquet/crates/tarball/src/lib.rs

@@ -1828,7 +1828,7 @@ pub fn download_priority(unpacked_size: Option<usize>, file_count: Option<usize>
 // hinting, store_dir + retry_opts are install-scoped, and
 // ignore_file_pattern is the per-fetch archive filter. Bundling
 // into a struct would just push the same fields into a wrapper.
-#[allow(
+#[expect(
     clippy::too_many_arguments,
     reason = "the parameters are independent install-scoped inputs; bundling them into a struct only moves the same fields into a wrapper"
 )]
@@ -2378,13 +2378,9 @@ fn manifest_package_id(manifest: Option<&serde_json::Value>) -> Option<String> {
 /// `addFilesFromDir` does on each tempdir file).
 // 8 arguments — over the default clippy threshold, but each is
 // distinct (see the matching note on `fetch_and_extract_zip_with_retry`).
-#[allow(
-    clippy::too_many_arguments,
-    reason = "the parameters are independent install-scoped inputs; bundling them into a struct only moves the same fields into a wrapper"
-)]
 #[expect(
     clippy::too_many_arguments,
-    reason = "arg count is set by upstream pnpm's fetcher signature"
+    reason = "the parameters are independent install-scoped inputs; bundling them into a struct only moves the same fields into a wrapper"
 )]
 async fn fetch_and_extract_zip_once<Reporter: self::Reporter>(
     http_client: &ThrottledClient,

pacquet/tasks/integrated-benchmark/src/cli_args.rs

@@ -178,7 +178,7 @@ pub enum RegistryMode {
 // will stop firing once the `Hoisted*` and `Pnp*` linker buckets land.
 // Keeping the prefix is intentional — it mirrors the slug's leading
 // segment and makes the linker grouping legible in code.
-#[allow(
+#[expect(
     clippy::enum_variant_names,
     reason = "the shared `Isolated` prefix mirrors the scenario slug and keeps the linker grouping legible; it stops firing once other linker buckets land"
 )]