Clean up low-severity code quality issues

- Share IMAGE_EXTENSIONS between discovery.rs and watcher.rs (DRY)
- Extract compute_renamed_path() to deduplicate ~100 lines in executor
- Extract estimate_text_dimensions() to deduplicate watermark calc (3 copies)
- Fix encoder fallback defaults: WebP 85, AVIF 63 (match QualityPreset::High)
- Extract watch_config_dir() and load_watches() helpers in CLI (4 copies)
- Remove redundant else branches after unwrap_or_default()
- Rename misleading chrono_timestamp() to unix_timestamp()

pixstrip-cli/src/main.rs

@@ -9,6 +9,20 @@ use pixstrip_core::types::*;
 use std::io::Write;
 use std::path::PathBuf;
 
+fn watch_config_dir() -> PathBuf {
+    dirs::config_dir()
+        .or_else(|| dirs::home_dir().map(|h| h.join(".config")))
+        .unwrap_or_else(|| std::env::temp_dir())
+        .join("pixstrip")
+}
+
+fn load_watches(watches_path: &std::path::Path) -> Vec<pixstrip_core::watcher::WatchFolder> {
+    std::fs::read_to_string(watches_path)
+        .ok()
+        .and_then(|s| serde_json::from_str(&s).ok())
+        .unwrap_or_default()
+}
+
 #[derive(Parser)]
 #[command(name = "pixstrip")]
 #[command(about = "Batch image processor - resize, convert, compress, strip metadata, watermark, and rename")]
@@ -440,7 +454,7 @@ fn cmd_process(args: CmdProcessArgs) {
     // Save to history - use actual output paths from the executor
     let history = HistoryStore::new();
     if let Err(e) = history.add(pixstrip_core::storage::HistoryEntry {
-        timestamp: chrono_timestamp(),
+        timestamp: unix_timestamp(),
         input_dir: input_dir.canonicalize().unwrap_or_else(|_| input_dir.to_path_buf()).to_string_lossy().into(),
         output_dir: output_dir.canonicalize().unwrap_or_else(|_| output_dir.to_path_buf()).to_string_lossy().into(),
         preset_name: args.preset,
@@ -640,19 +654,9 @@ fn cmd_watch_add(path: &str, preset_name: &str, recursive: bool) {
     };
 
     // Store in config
-    let config_dir = dirs::config_dir()
-        .or_else(|| dirs::home_dir().map(|h| h.join(".config")))
-        .unwrap_or_else(|| std::env::temp_dir())
-        .join("pixstrip");
+    let config_dir = watch_config_dir();
     let watches_path = config_dir.join("watches.json");
-    let mut watches: Vec<pixstrip_core::watcher::WatchFolder> = if watches_path.exists() {
-        std::fs::read_to_string(&watches_path)
-            .ok()
-            .and_then(|s| serde_json::from_str(&s).ok())
-            .unwrap_or_default()
-    } else {
-        Vec::new()
-    };
+    let mut watches = load_watches(&watches_path);
 
     // Don't add duplicate paths
     if watches.iter().any(|w| w.path == watch.path) {
@@ -682,20 +686,10 @@ fn cmd_watch_add(path: &str, preset_name: &str, recursive: bool) {
 }
 
 fn cmd_watch_list() {
-    let config_dir = dirs::config_dir()
-        .or_else(|| dirs::home_dir().map(|h| h.join(".config")))
-        .unwrap_or_else(|| std::env::temp_dir())
-        .join("pixstrip");
+    let config_dir = watch_config_dir();
     let watches_path = config_dir.join("watches.json");
 
-    let watches: Vec<pixstrip_core::watcher::WatchFolder> = if watches_path.exists() {
-        std::fs::read_to_string(&watches_path)
-            .ok()
-            .and_then(|s| serde_json::from_str(&s).ok())
-            .unwrap_or_default()
-    } else {
-        Vec::new()
-    };
+    let watches = load_watches(&watches_path);
 
     if watches.is_empty() {
         println!("No watch folders configured.");
@@ -718,20 +712,10 @@ fn cmd_watch_list() {
 }
 
 fn cmd_watch_remove(path: &str) {
-    let config_dir = dirs::config_dir()
-        .or_else(|| dirs::home_dir().map(|h| h.join(".config")))
-        .unwrap_or_else(|| std::env::temp_dir())
-        .join("pixstrip");
+    let config_dir = watch_config_dir();
     let watches_path = config_dir.join("watches.json");
 
-    let mut watches: Vec<pixstrip_core::watcher::WatchFolder> = if watches_path.exists() {
-        std::fs::read_to_string(&watches_path)
-            .ok()
-            .and_then(|s| serde_json::from_str(&s).ok())
-            .unwrap_or_default()
-    } else {
-        Vec::new()
-    };
+    let mut watches = load_watches(&watches_path);
 
     let original_len = watches.len();
     let target = PathBuf::from(path);
@@ -759,10 +743,7 @@ fn cmd_watch_remove(path: &str) {
 }
 
 fn cmd_watch_start() {
-    let config_dir = dirs::config_dir()
-        .or_else(|| dirs::home_dir().map(|h| h.join(".config")))
-        .unwrap_or_else(|| std::env::temp_dir())
-        .join("pixstrip");
+    let config_dir = watch_config_dir();
     let watches_path = config_dir.join("watches.json");
 
     let watches: Vec<pixstrip_core::watcher::WatchFolder> = if watches_path.exists() {
@@ -876,7 +857,7 @@ fn cmd_watch_start() {
                             println!("  Processed: {} -> {}", format_bytes(r.total_input_bytes), format_bytes(r.total_output_bytes));
                             let history = HistoryStore::new();
                             let _ = history.add(pixstrip_core::storage::HistoryEntry {
-                                timestamp: chrono_timestamp(),
+                                timestamp: unix_timestamp(),
                                 input_dir: input_dir.to_string_lossy().into(),
                                 output_dir: output_dir.to_string_lossy().into(),
                                 preset_name: Some(preset_name.to_string()),
@@ -1065,7 +1046,7 @@ fn format_duration(ms: u64) -> String {
     }
 }
 
-fn chrono_timestamp() -> String {
+fn unix_timestamp() -> String {
     // Store as Unix seconds string (must match GTK format for pruning compatibility)
     std::time::SystemTime::now()
         .duration_since(std::time::UNIX_EPOCH)