feat(omo): improve agent model selection UX and fix lowercase keys (#1004)

* fix(omo): use lowercase keys for builtin agent definitions

OMO config schema expects all agent keys to be lowercase.
Updated OMO_BUILTIN_AGENTS keys (Sisyphus → sisyphus, Hephaestus →
hephaestus, etc.) and aligned Rust test fixtures accordingly.

* feat(omo): add i18n support and tooltips for agent/category descriptions

* feat(omo): add preset model variants for thinking level support

Add OPENCODE_PRESET_MODEL_VARIANTS constant with variant definitions
for Google, OpenAI, and Anthropic models. The omoModelVariantsMap
builder now falls back to presets when config-defined variants are
absent, enabling the variant selector for supported models.

* feat(omo): replace model select with searchable combobox and improve fallback handling

* feat(omo): enrich preset model defaults and metadata fallback

* fix(omo): preserve custom fields and align otherFields import/validation

* fix: resolve omo clippy warnings and include app update

src-tauri/src/commands/misc.rs

@@ -323,7 +323,7 @@ fn scan_cli_version(tool: &str) -> (Option<String>, Option<String>) {
     let mut search_paths: Vec<std::path::PathBuf> = vec![
         home.join(".local/bin"), // Native install (official recommended)
         home.join(".npm-global/bin"),
-        home.join("n/bin"), // n version manager
+        home.join("n/bin"),      // n version manager
         home.join(".volta/bin"), // Volta package manager
     ];