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/app/mode/editor.rs

@@ -66,7 +66,7 @@ impl EditorState {
             self.cursor_line += 1;
         }
         self.cursor_col = self.cursor_col.min(
-            self.content.get(self.cursor_line).map(|l| l.len()).unwrap_or(0),
+            self.content.get(self.cursor_line).map_or(0, std::string::String::len),
         );
     }
 
@@ -112,7 +112,7 @@ impl EditorState {
 /// Flow: no-op if no editor is open → for each char: `\n`/`\r` inserts a
 /// line and moves down, `\t` inserts two spaces, everything else inserts
 /// the char directly → mark state dirty.
-pub fn handle_editor_input(state: &mut AppStateRest, text: String) {
+pub fn handle_editor_input(state: &mut AppStateRest, text: &str) {
     let editor = &mut state.misc.editor;
     if editor.is_none() {
         return;