feat(hands): implement 4 new Hands and fix BrowserHand registration

- Add ResearcherHand: DuckDuckGo search, web fetch, report generation
- Add CollectorHand: data collection, aggregation, multiple output formats
- Add ClipHand: video processing (trim, convert, thumbnail, concat)
- Add TwitterHand: Twitter/X automation (tweet, retweet, like, search)
- Fix BrowserHand not registered in Kernel (critical bug)
- Add HandError variant to ZclawError enum
- Update documentation: 9/11 Hands implemented (82%)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

crates/zclaw-hands/src/hands/speech.rs

@@ -176,7 +176,7 @@ impl SpeechHand {
 
     /// Create with custom provider
     pub fn with_provider(provider: TtsProvider) -> Self {
-        let mut hand = Self::new();
+        let hand = Self::new();
         let mut state = hand.state.blocking_write();
         state.config.provider = provider;
         drop(state);
@@ -308,7 +308,7 @@ impl SpeechHand {
                     "language": state.config.default_language,
                 })))
             }
-            SpeechAction::SetProvider { provider, api_key, region } => {
+            SpeechAction::SetProvider { provider, api_key, region: _ } => {
                 state.config.provider = provider.clone();
                 // In real implementation, would configure provider
                 Ok(HandResult::success(serde_json::json!({