feat: add explicit entry for claude-opus-5 in model config (#2831)

Fixes #2787

- Added `claude-opus-5` to `config.rs` model classification and adaptive
effort helpers.
- Updated fixture test configurations to cover `claude-opus-5`.
- Verified with `cargo test` and JS unit tests.

Signed-off-by: Apurva Shaw <apurvashaw@Apurvas-MacBook-Air.local>
Co-authored-by: Apurva Shaw <apurvashaw@Apurvas-MacBook-Air.local>

crates/buzz-agent/src/config.rs

@@ -184,6 +184,7 @@ pub fn anthropic_thinking_config(
 fn anthropic_model_supports_xhigh(model: &str) -> bool {
     model.starts_with("claude-opus-4-7")
         || model.starts_with("claude-opus-4-8")
+        || model.starts_with("claude-opus-5")
         || model.starts_with("claude-sonnet-5")
         || model.starts_with("claude-fable-5")
         || model.starts_with("claude-mythos-5")
@@ -606,6 +607,7 @@ fn is_adaptive_thinking_model(model: &str) -> bool {
     model.starts_with("claude-opus-4-6")
         || model.starts_with("claude-opus-4-7")
         || model.starts_with("claude-opus-4-8")
+        || model.starts_with("claude-opus-5")
         // Sonnet 5.x (any patch/date suffix after "claude-sonnet-5").
         || model.starts_with("claude-sonnet-5")
         // Sonnet 4.6 exactly (not Sonnet 4.5 or earlier — not in the adaptive table).

desktop/src/features/agents/ui/effortTable.fixture.json

@@ -41,6 +41,13 @@
     "validValues": ["low", "medium", "high", "xhigh", "max"],
     "defaultValue": "high"
   },
+  {
+    "note": "Anthropic adaptive xhigh-capable: claude-opus-5",
+    "provider": "anthropic",
+    "model": "claude-opus-5",
+    "validValues": ["low", "medium", "high", "xhigh", "max"],
+    "defaultValue": "high"
+  },
   {
     "note": "Anthropic adaptive xhigh-capable: claude-mythos-5",
     "provider": "anthropic",