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.

src/agents/AGENTS.md

@@ -11,7 +11,7 @@ Agent factories following `createXXXAgent(model) → AgentConfig` pattern. Each
 | Agent | Model | Temp | Mode | Fallback Chain | Purpose |
 |-------|-------|------|------|----------------|---------|
 | **Sisyphus** | claude-opus-4-6 max | 0.1 | all | k2p5 → kimi-k2.5 → gpt-5.4 medium → glm-5 → big-pickle | Main orchestrator, plans + delegates |
-| **Hephaestus** | gpt-5.3-codex medium | 0.1 | all | gpt-5.4 medium (copilot) | Autonomous deep worker |
+| **Hephaestus** | gpt-5.4 medium | 0.1 | all | — | Autonomous deep worker |
 | **Oracle** | gpt-5.4 high | 0.1 | subagent | gemini-3.1-pro high → claude-opus-4-6 max | Read-only consultation |
 | **Librarian** | minimax-m2.7 | 0.1 | subagent | minimax-m2.7-highspeed → claude-haiku-4-5 → gpt-5-nano | External docs/code search |
 | **Explore** | grok-code-fast-1 | 0.1 | subagent | minimax-m2.7-highspeed → minimax-m2.7 → claude-haiku-4-5 → gpt-5-nano | Contextual grep |

src/cli/__snapshots__/model-fallback.test.ts.snap

@@ -202,7 +202,7 @@ exports[`generateModelConfig single native provider uses OpenAI models when only
       "variant": "medium",
     },
     "hephaestus": {
-      "model": "openai/gpt-5.3-codex",
+      "model": "openai/gpt-5.4",
       "variant": "medium",
     },
     "librarian": {
@@ -287,7 +287,7 @@ exports[`generateModelConfig single native provider uses OpenAI models with isMa
       "variant": "medium",
     },
     "hephaestus": {
-      "model": "openai/gpt-5.3-codex",
+      "model": "openai/gpt-5.4",
       "variant": "medium",
     },
     "librarian": {
@@ -490,7 +490,7 @@ exports[`generateModelConfig all native providers uses preferred models from fal
       "model": "anthropic/claude-haiku-4-5",
     },
     "hephaestus": {
-      "model": "openai/gpt-5.3-codex",
+      "model": "openai/gpt-5.4",
       "variant": "medium",
     },
     "metis": {
@@ -565,7 +565,7 @@ exports[`generateModelConfig all native providers uses preferred models with isM
       "model": "anthropic/claude-haiku-4-5",
     },
     "hephaestus": {
-      "model": "openai/gpt-5.3-codex",
+      "model": "openai/gpt-5.4",
       "variant": "medium",
     },
     "metis": {
@@ -641,7 +641,7 @@ exports[`generateModelConfig fallback providers uses OpenCode Zen models when on
       "model": "opencode/claude-haiku-4-5",
     },
     "hephaestus": {
-      "model": "opencode/gpt-5.3-codex",
+      "model": "opencode/gpt-5.4",
       "variant": "medium",
     },
     "metis": {
@@ -716,7 +716,7 @@ exports[`generateModelConfig fallback providers uses OpenCode Zen models with is
       "model": "opencode/claude-haiku-4-5",
     },
     "hephaestus": {
-      "model": "opencode/gpt-5.3-codex",
+      "model": "opencode/gpt-5.4",
       "variant": "medium",
     },
     "metis": {
@@ -1049,7 +1049,7 @@ exports[`generateModelConfig mixed provider scenarios uses Claude + OpenCode Zen
       "model": "anthropic/claude-haiku-4-5",
     },
     "hephaestus": {
-      "model": "opencode/gpt-5.3-codex",
+      "model": "opencode/gpt-5.4",
       "variant": "medium",
     },
     "metis": {
@@ -1124,7 +1124,7 @@ exports[`generateModelConfig mixed provider scenarios uses OpenAI + Copilot comb
       "model": "github-copilot/gpt-5-mini",
     },
     "hephaestus": {
-      "model": "openai/gpt-5.3-codex",
+      "model": "openai/gpt-5.4",
       "variant": "medium",
     },
     "metis": {
@@ -1329,7 +1329,7 @@ exports[`generateModelConfig mixed provider scenarios uses all fallback provider
       "model": "opencode/claude-haiku-4-5",
     },
     "hephaestus": {
-      "model": "opencode/gpt-5.3-codex",
+      "model": "github-copilot/gpt-5.4",
       "variant": "medium",
     },
     "librarian": {
@@ -1407,7 +1407,7 @@ exports[`generateModelConfig mixed provider scenarios uses all providers togethe
       "model": "anthropic/claude-haiku-4-5",
     },
     "hephaestus": {
-      "model": "openai/gpt-5.3-codex",
+      "model": "openai/gpt-5.4",
       "variant": "medium",
     },
     "librarian": {
@@ -1485,7 +1485,7 @@ exports[`generateModelConfig mixed provider scenarios uses all providers with is
       "model": "anthropic/claude-haiku-4-5",
     },
     "hephaestus": {
-      "model": "openai/gpt-5.3-codex",
+      "model": "openai/gpt-5.4",
       "variant": "medium",
     },
     "librarian": {

src/cli/model-fallback.test.ts

@@ -458,7 +458,7 @@ describe("generateModelConfig", () => {
       const result = generateModelConfig(config)
 
       // #then
-      expect(result.agents?.hephaestus?.model).toBe("openai/gpt-5.3-codex")
+      expect(result.agents?.hephaestus?.model).toBe("openai/gpt-5.4")
       expect(result.agents?.hephaestus?.variant).toBe("medium")
     })
 
@@ -484,7 +484,7 @@ describe("generateModelConfig", () => {
       const result = generateModelConfig(config)
 
       // #then
-      expect(result.agents?.hephaestus?.model).toBe("opencode/gpt-5.3-codex")
+      expect(result.agents?.hephaestus?.model).toBe("opencode/gpt-5.4")
       expect(result.agents?.hephaestus?.variant).toBe("medium")
     })
 

src/shared/agent-variant.test.ts

@@ -113,9 +113,9 @@ describe("resolveVariantForModel", () => {
   })
 
   test("returns correct variant for openai provider (hephaestus agent)", () => {
-    // #given hephaestus has openai/gpt-5.3-codex with variant "medium" in its chain
+    // #given hephaestus has openai/gpt-5.4 with variant "medium" in its chain
     const config = {} as OhMyOpenCodeConfig
-    const model = { providerID: "openai", modelID: "gpt-5.3-codex" }
+    const model = { providerID: "openai", modelID: "gpt-5.4" }
 
     // #when
     const variant = resolveVariantForModel(config, "hephaestus", model)