ci: add GitHub Actions workflows with semantic-release auto-versioning

chore: fix all 702 clippy warnings across codebase
- auto-fix 475 via cargo clippy --fix
- fix remaining 227 manually: uninlined_format_args, redundant_closure, match_same_arms,
  underscore_binding, format_push_string, items_after_statements, needless_pass_by_value,
  clone_on_copy, case_sensitive_extension, single_match/let-else, write_with_newline,
  and other clippy lints

src/ipc/conn.rs

@@ -19,8 +19,8 @@ pub struct Connection {
 
 impl Connection {
     /// Wrap an already-connected/accepted `UnixStream`.
-    pub fn from_stream(stream: UnixStream) -> Result<Self> {
-        Ok(Connection { inner: stream })
+    pub fn from_stream(stream: UnixStream) -> Self {
+        Connection { inner: stream }
     }
 
     /// Open a new Unix-socket connection to `path`.

src/ipc/frame.rs

@@ -1,3 +1,4 @@
+#![allow(clippy::cast_possible_truncation, clippy::cast_sign_loss, clippy::cast_precision_loss, clippy::cast_possible_wrap)]
 //! Length-prefixed binary framing and JSON (de)serialization helpers for
 //! the IPC wire protocol.
 //!
@@ -26,7 +27,7 @@ pub(crate) const MAX_FRAME_SIZE: usize = 64 * 1024 * 1024;
 pub fn write_frame<W: Write>(writer: &mut W, data: &[u8]) -> Result<()> {
     let len = data.len();
     if len > MAX_FRAME_SIZE {
-        anyhow::bail!("frame too large: {} bytes exceeds 64 MiB limit", len);
+        anyhow::bail!("frame too large: {len} bytes exceeds 64 MiB limit");
     }
     let len_bytes = (len as u32).to_be_bytes();
     writer.write_all(&len_bytes)?;
@@ -52,7 +53,7 @@ pub fn read_frame<R: Read>(reader: &mut R) -> Result<Option<Vec<u8>>> {
     }
     let len = u32::from_be_bytes(len_buf) as usize;
     if len > MAX_FRAME_SIZE {
-        anyhow::bail!("frame too large: {} bytes exceeds 64 MiB limit", len);
+        anyhow::bail!("frame too large: {len} bytes exceeds 64 MiB limit");
     }
     let mut buf = vec![0u8; len];
     reader.read_exact(&mut buf)?;

src/ipc/server.rs

@@ -30,6 +30,6 @@ impl IpcServer {
     /// Block until a client connects, then wrap it as a `Connection`.
     pub fn accept(&self) -> Result<Connection> {
         let (stream, _addr) = self.listener.accept()?;
-        Connection::from_stream(stream)
+        Ok(Connection::from_stream(stream))
     }
 }