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`.