Fix code quality: trailing whitespace, unused imports, clippy warnings

- Fix trailing whitespace in kex.rs and s3.rs
- Add missing KexProposal import in kex_complete.rs
- Auto-fix clippy warnings across all crates
- All 153 tests pass

markbase-core/src/archive/warning.rs

@@ -1,6 +1,6 @@
 // Warning System - Legal and Technical Warnings for Optional Formats
 
-use log::{warn, info};
+use log::{info, warn};
 
 use crate::archive::config::ArchiveConfig;
 
@@ -63,25 +63,27 @@ pub fn show_startup_warnings(config: &ArchiveConfig) {
     if config.enable_rar {
         show_rar_legal_warning();
     }
-    
+
     if config.enable_xz {
         // Dependency check happens in ProcessorRegistry
     }
-    
+
     if config.enable_7z {
         show_7z_stability_warning();
     }
-    
+
     // Show summary of enabled formats
-    let enabled_optional = [
-        config.enable_rar,
-        config.enable_xz,
-        config.enable_7z,
-    ].iter().filter(|&x| *x).count();
-    
+    let enabled_optional = [config.enable_rar, config.enable_xz, config.enable_7z]
+        .iter()
+        .filter(|&x| *x)
+        .count();
+
     if enabled_optional > 0 {
         info!("");
-        info!("⚠️ {} optional format(s) enabled with warnings shown above", enabled_optional);
+        info!(
+            "⚠️ {} optional format(s) enabled with warnings shown above",
+            enabled_optional
+        );
         info!("Core formats (9): ZIP, TAR, GZIP, ZSTD, BZIP2, LZ4, TAR.GZ, TAR.BZ2, TAR.ZST");
         info!("");
     }
@@ -89,8 +91,7 @@ pub fn show_startup_warnings(config: &ArchiveConfig) {
 
 /// Generate user-facing legal disclaimer text
 pub fn generate_rar_legal_disclaimer() -> String {
-    format!(
-        "RAR FORMAT LEGAL DISCLAIMER
+    "RAR FORMAT LEGAL DISCLAIMER
 
 IMPORTANT WARNING:
 
@@ -136,6 +137,5 @@ CONTACT:
 Last Updated: 2026-06-10
 Version: 1.0
 Legal Consultation: [Please consult professional lawyer for commercial use]
-"
-    )
-}
+".to_string()
+}