chore(lint): clean up clippy warnings across workspace

Auto-applied cargo clippy --fix across 11 files — needless return,
unnecessary cast, map_or simplification, repeat().take() → repeat_n(),
iter().any() → contains(), manual char comparison, lifetime elision,
push_str single-char, reference immediately dereferenced.

Also fixed three lints on file_storage.rs manually: two doc-list-item
overindentations, plus the same needless-return. Baseline main was
not clippy-clean with -D warnings before; after this pass one
needless_range_loop warning remains (live.rs:1089) that clippy's
suggested rewrite would make less readable — left for a dedicated
refactor session.

Build + workspace tests remain green (245 passing, 0 failing, 1
ignored).

src-tauri/src/commands/diagnostics.rs

@@ -247,7 +247,7 @@ pub async fn generate_diagnostic_report(
         .map(|d| d.as_secs())
         .unwrap_or(0);
     out.push_str(&format!("- Generated: unix `{}`\n", now));
-    out.push_str("\n");
+    out.push('\n');
     out.push_str(
         "> This report is local-only until you choose to share it. \
                   Review the contents below before sending to anyone.\n\n",

src-tauri/src/commands/live.rs

@@ -1155,12 +1155,10 @@ fn longest_common_token_subsequence(a: &[&str], b: &[&str]) -> usize {
 }
 
 fn is_low_signal_token(token: &str) -> bool {
-    LOW_SIGNAL_TOKENS
-        .iter()
-        .any(|low_signal| *low_signal == token)
+    LOW_SIGNAL_TOKENS.contains(&token)
 }
 
-fn meaningful_tokens<'a>(text: &'a str) -> Vec<&'a str> {
+fn meaningful_tokens(text: &str) -> Vec<&str> {
     text.split_whitespace()
         .filter(|token| !token.is_empty() && token.len() > 1 && !is_low_signal_token(token))
         .collect()

src-tauri/src/commands/models.rs

@@ -412,7 +412,7 @@ pub fn detect_active_compute_device() -> ActiveComputeDevice {
                 reason: None,
             };
         }
-        return ActiveComputeDevice {
+        ActiveComputeDevice {
             kind: "cpu".into(),
             label: "CPU (fallback)".into(),
             reason: Some(
@@ -420,7 +420,7 @@ pub fn detect_active_compute_device() -> ActiveComputeDevice {
                  libvulkan1 (Linux) to enable GPU acceleration."
                     .into(),
             ),
-        };
+        }
     }
 }
 

src-tauri/src/commands/paste.rs

@@ -345,7 +345,7 @@ fn classify_terminal(raw: &str) -> Option<String> {
 fn detect_focused_window_class() -> Option<String> {
     #[cfg(target_os = "linux")]
     {
-        return detect_focused_window_class_linux();
+        detect_focused_window_class_linux()
     }
     #[cfg(target_os = "macos")]
     {