docs: update hephaestus default model references from gpt-5.3-codex to gpt-5.4

Updated across README (all locales), docs/guide/, docs/reference/,
docs/examples/, AGENTS.md files, and test expectations/snapshots.

The deep category and multimodal-looker still use gpt-5.3-codex as
those are separate from the hephaestus agent.

README.md

@@ -164,7 +164,7 @@ Even only with following subscriptions, ultrawork will work well (this project i
 
 **Sisyphus** (`claude-opus-4-6` / **`kimi-k2.5`** / **`glm-5`** ) is your main orchestrator. He plans, delegates to specialists, and drives tasks to completion with aggressive parallel execution. He does not stop halfway.
 
-**Hephaestus** (`gpt-5.3-codex`) is your autonomous deep worker. Give him a goal, not a recipe. He explores the codebase, researches patterns, and executes end-to-end without hand-holding. *The Legitimate Craftsman.*
+**Hephaestus** (`gpt-5.4`) is your autonomous deep worker. Give him a goal, not a recipe. He explores the codebase, researches patterns, and executes end-to-end without hand-holding. *The Legitimate Craftsman.*
 
 **Prometheus** (`claude-opus-4-6` / **`kimi-k2.5`** / **`glm-5`** ) is your strategic planner. Interview mode: it questions, identifies scope, and builds a detailed plan before a single line of code is touched.
 
@@ -172,7 +172,7 @@ Every agent is tuned to its model's specific strengths. No manual model-juggling
 
 > Anthropic [blocked OpenCode because of us.](https://x.com/thdxr/status/2010149530486911014) That's why Hephaestus is called "The Legitimate Craftsman." The irony is intentional.
 >
-> We run best on Opus, but Kimi K2.5 + GPT-5.3 Codex already beats vanilla Claude Code. Zero config needed.
+> We run best on Opus, but Kimi K2.5 + GPT-5.4 already beats vanilla Claude Code. Zero config needed.
 
 ### Agent Orchestration