feat(categories): change quick category default model from claude-haiku-4-5 to gpt-5.4-mini

GPT-5.4-mini provides stronger reasoning at comparable speed and cost.
Haiku remains as the next fallback priority in the chain.

Changes:
- DEFAULT_CATEGORIES quick model: anthropic/claude-haiku-4-5 → openai/gpt-5.4-mini
- Fallback chain: gpt-5.4-mini → haiku → gemini-3-flash → minimax-m2.5 → gpt-5-nano
- OpenAI-only catalog: quick uses gpt-5.4-mini directly
- Think-mode: add gpt-5-4-mini and gpt-5-4-nano high variants
- Update all documentation references

src/hooks/think-mode/switcher.test.ts

@@ -53,6 +53,22 @@ describe("think-mode switcher", () => {
         expect(variant).toBe("gpt-5-4-high")
       })
 
+      it("should handle gpt-5.4-mini model", () => {
+        // given a GPT-5.4-mini model ID
+        const variant = getHighVariant("gpt-5.4-mini")
+
+        // then should return high variant
+        expect(variant).toBe("gpt-5-4-mini-high")
+      })
+
+      it("should handle gpt-5.4-nano model", () => {
+        // given a GPT-5.4-nano model ID
+        const variant = getHighVariant("gpt-5.4-nano")
+
+        // then should return high variant
+        expect(variant).toBe("gpt-5-4-nano-high")
+      })
+
       it("should handle dots in GPT-5.1 codex variants", () => {
         // given a GPT-5.1-codex model ID
         const variant = getHighVariant("gpt-5.1-codex")

src/hooks/think-mode/switcher.ts

@@ -65,6 +65,8 @@ const HIGH_VARIANT_MAP: Record<string, string> = {
   "gpt-5-4": "gpt-5-4-high",
   "gpt-5-4-chat-latest": "gpt-5-4-chat-latest-high",
   "gpt-5-4-pro": "gpt-5-4-pro-high",
+  "gpt-5-4-mini": "gpt-5-4-mini-high",
+  "gpt-5-4-nano": "gpt-5-4-nano-high",
   // Antigravity (Google)
   "antigravity-gemini-3-1-pro": "antigravity-gemini-3-1-pro-high",
   "antigravity-gemini-3-flash": "antigravity-gemini-3-flash-high",