refactor(fspy): own macOS shared-memory mapping

Cargo.toml

@@ -123,7 +123,6 @@ serde = "1.0.219"
 serde_json = "1.0.140"
 serde_norway = "0.9.42"
 sha2 = "0.11.0"
-shared_memory = "0.12.4"
 shell-escape = "0.1.5"
 similar = "3.0.0"
 smallvec = { version = "2.0.0-alpha.12", features = ["std"] }

crates/fspy_shared/src/ipc/channel/mod.rs

@@ -114,7 +114,7 @@ impl Deref for Sender {
 }
 
 #[cfg_attr(
-    not(target_os = "linux"),
+    target_os = "windows",
     expect(
         clippy::non_send_fields_in_send_ty,
         reason = "`Sender` holds a shared file lock that ensures there's no reader, so `shm` can be safely written to"
@@ -135,7 +135,7 @@ pub struct Receiver {
 }
 
 #[cfg_attr(
-    not(target_os = "linux"),
+    target_os = "windows",
     expect(
         clippy::non_send_fields_in_send_ty,
         reason = "Receiver doesn't read or write `shm`. It only passes it to `ReceiverLockGuard` under the lock"

crates/fspy_shm/Cargo.toml

@@ -7,9 +7,6 @@ license.workspace = true
 publish = false
 rust-version.workspace = true
 
-[target.'cfg(not(any(target_os = "linux", target_os = "windows")))'.dependencies]
-shared_memory = { workspace = true, features = ["logging"] }
-
 [target.'cfg(target_os = "linux")'.dependencies]
 memmap2 = { workspace = true }
 passfd = { workspace = true, features = ["async"] }
@@ -19,6 +16,12 @@ tokio-util = { workspace = true }
 tracing = { workspace = true }
 uuid = { workspace = true, features = ["v4"] }
 
+[target.'cfg(target_os = "macos")'.dependencies]
+base64 = { workspace = true }
+memmap2 = { workspace = true }
+rustix = { workspace = true, features = ["fs", "shm"] }
+uuid = { workspace = true, features = ["v4"] }
+
 [target.'cfg(target_os = "windows")'.dependencies]
 uuid = { workspace = true, features = ["v4"] }
 windows-sys = { workspace = true, features = [

crates/fspy_shm/README.md

@@ -34,6 +34,7 @@ The channel hides that difference with its lock file. [`ChannelConf::sender`](..
 Each platform keeps its implementation rationale beside its source:
 
 - [Linux: `memfd` with a descriptor broker](src/linux/README.md)
+- [macOS: named POSIX shared memory](src/macos/README.md)
 - [Windows: sparse file-backed named mapping](src/windows/README.md)
 
-At this point in the stack, macOS still delegates mapping creation and opening to the [`shared_memory`](https://crates.io/crates/shared_memory) crate.
+All implementations provide the API above. Their identifiers and operating system objects differ. Each platform README explains the chosen API and why the previous `shared_memory` backend did not meet its requirements.