fix(model-resolver): return variant from fallback chain, handle model name normalization

- Add variant to ModelResolutionResult return type
- Return variant from matched fallback entry
- Add normalizeModelName() for Claude model hyphen/period differences
- Add transformModelForProvider() for github-copilot model names
- Update delegate-task to use resolved variant (user config takes priority)
- Fix test expectations for new fallback behavior

src/cli/config-manager.test.ts

@@ -256,7 +256,7 @@ describe("generateOmoConfig - model fallback system", () => {
     // #when generating config
     const result = generateOmoConfig(config)
 
-    // #then should use github-copilot sonnet models
+    // #then should use github-copilot sonnet models (copilot fallback)
     expect((result.agents as Record<string, { model: string }>).Sisyphus.model).toBe("github-copilot/claude-sonnet-4.5")
   })
 
@@ -318,8 +318,8 @@ describe("generateOmoConfig - model fallback system", () => {
 
     // #then Sisyphus should use native OpenAI (fallback within native tier)
     expect((result.agents as Record<string, { model: string }>).Sisyphus.model).toBe("openai/gpt-5.2")
-    // #then Oracle should use native OpenAI (primary for ultrabrain)
-    expect((result.agents as Record<string, { model: string }>).oracle.model).toBe("openai/gpt-5.2-codex")
+    // #then Oracle should use native OpenAI (first fallback entry)
+    expect((result.agents as Record<string, { model: string }>).oracle.model).toBe("openai/gpt-5.2")
     // #then multimodal-looker should use native OpenAI (fallback within native tier)
     expect((result.agents as Record<string, { model: string }>)["multimodal-looker"].model).toBe("openai/gpt-5.2")
   })