feat(command-palette): add fuzzy model/provider filtering, expose ModelPaletteEntry, and show active model with provider in UI header

- Introduce `ModelPaletteEntry` and re‑export it for external use.
- Extend `CommandPalette` with dynamic sources (models, providers) and methods to refresh suggestions based on `:model` and `:provider` prefixes.
- Implement fuzzy matching via `match_score` and subsequence checks for richer suggestion ranking.
- Add `provider` command spec and completions.
- Update UI to display “Model (Provider)” in the header and use the new active model label helper.
- Wire catalog updates throughout `ChatApp` (model palette entries, command palette refresh on state changes, model picker integration).

crates/owlen-tui/src/commands/mod.rs

@@ -80,6 +80,10 @@ const COMMANDS: &[CommandSpec] = &[
         keyword: "model",
         description: "Select a model",
     },
+    CommandSpec {
+        keyword: "provider",
+        description: "Switch active provider",
+    },
     CommandSpec {
         keyword: "model info",
         description: "Show detailed information for a model",
@@ -177,7 +181,6 @@ pub fn suggestions(input: &str) -> Vec<String> {
     if trimmed.is_empty() {
         return default_suggestions();
     }
-
     COMMANDS
         .iter()
         .filter_map(|spec| {
@@ -189,3 +192,52 @@ pub fn suggestions(input: &str) -> Vec<String> {
         })
         .collect()
 }
+
+pub fn match_score(candidate: &str, query: &str) -> Option<(usize, usize)> {
+    let query = query.trim();
+    if query.is_empty() {
+        return Some((usize::MAX, candidate.len()));
+    }
+
+    let candidate_normalized = candidate.trim().to_lowercase();
+    if candidate_normalized.is_empty() {
+        return None;
+    }
+
+    let query_normalized = query.to_lowercase();
+
+    if candidate_normalized == query_normalized {
+        Some((0, candidate.len()))
+    } else if candidate_normalized.starts_with(&query_normalized) {
+        Some((1, candidate.len()))
+    } else if let Some(pos) = candidate_normalized.find(&query_normalized) {
+        Some((2, pos))
+    } else if is_subsequence(&candidate_normalized, &query_normalized) {
+        Some((3, candidate.len()))
+    } else {
+        None
+    }
+}
+
+fn is_subsequence(text: &str, pattern: &str) -> bool {
+    if pattern.is_empty() {
+        return true;
+    }
+
+    let mut pattern_chars = pattern.chars();
+    let mut current = match pattern_chars.next() {
+        Some(ch) => ch,
+        None => return true,
+    };
+
+    for ch in text.chars() {
+        if ch == current {
+            match pattern_chars.next() {
+                Some(next_ch) => current = next_ch,
+                None => return true,
+            }
+        }
+    }
+
+    false
+}