refactor(models): update agent/category fallback chains

- quick: replace openai fallback with opencode/grok-code
- writing: add zai-coding-plan/glm-4.7 between sonnet and gpt
- unspecified-low: gpt-5.2 → gpt-5.2-codex (medium)
- Sisyphus: add zai/glm-4.7 before openai, use gpt-5.2-codex (medium)
- Momus & Metis: add variant 'max' to gemini-3-pro
- explore: simplify to haiku (anthropic/opencode) → grok-code (opencode)

src/shared/model-requirements.test.ts

@@ -54,19 +54,19 @@ describe("AGENT_MODEL_REQUIREMENTS", () => {
     expect(primary.model).toBe("glm-4.7")
   })
 
-  test("explore has valid fallbackChain with gemini-3-flash-preview as primary", () => {
+  test("explore has valid fallbackChain with claude-haiku-4-5 as primary", () => {
     // #given - explore agent requirement
     const explore = AGENT_MODEL_REQUIREMENTS["explore"]
 
     // #when - accessing explore requirement
-    // #then - fallbackChain exists with gemini-3-flash-preview as first entry
+    // #then - fallbackChain exists with claude-haiku-4-5 as first entry
     expect(explore).toBeDefined()
     expect(explore.fallbackChain).toBeArray()
     expect(explore.fallbackChain.length).toBeGreaterThan(0)
 
     const primary = explore.fallbackChain[0]
-    expect(primary.providers).toContain("google")
-    expect(primary.model).toBe("gemini-3-flash-preview")
+    expect(primary.providers).toContain("anthropic")
+    expect(primary.model).toBe("claude-haiku-4-5")
   })
 
   test("multimodal-looker has valid fallbackChain with gemini-3-flash-preview as primary", () => {