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/cli/openai-only-model-catalog.ts

@@ -7,7 +7,7 @@ const OPENAI_ONLY_AGENT_OVERRIDES: Record<string, AgentConfig> = {
 
 const OPENAI_ONLY_CATEGORY_OVERRIDES: Record<string, CategoryConfig> = {
   artistry: { model: "openai/gpt-5.4", variant: "xhigh" },
-  quick: { model: "openai/gpt-5.3-codex", variant: "low" },
+  quick: { model: "openai/gpt-5.4-mini" },
   "visual-engineering": { model: "openai/gpt-5.4", variant: "high" },
   writing: { model: "openai/gpt-5.4", variant: "medium" },
 }