Add thinking notice + fix Venice auto-recover caching (#193)

Opt-in 💭 thinking-notice for slow text generation, plus a fix making Venice unsupported-field auto-recovery survive the per-message controller rebuild. Prepares 1.24.0.

Co-authored-by: Aine <aine@etke.cc>

src/agent/provider/entity/text_generation/prompt_variables.rs

@@ -1,6 +1,7 @@
 use chrono::{DateTime, Utc};
 use std::collections::HashMap;
 
+#[derive(Clone)]
 pub struct TextGenerationPromptVariables {
     map: HashMap<String, String>,
 }