feat(codex): declare gpt-5.6 context window for Claude Code takeover

- Update Codex OAuth presets to the gpt-5.6 family (haiku -> gpt-5.6-luna)
  and bump the custom Codex template default model
- Inject CLAUDE_CODE_MAX_CONTEXT_TOKENS / CLAUDE_CODE_AUTO_COMPACT_WINDOW
  (372000, the ChatGPT Codex catalog window with a ~353K effective budget,
  openai/codex#31860) into effective live settings so Claude Code stops
  assuming a 200K window and compacts before the upstream rejects the prompt
- Gate the injected defaults on every configured model being gpt-5.6*:
  gpt-5.5's upstream catalog oscillates between 272K and 372K and must not
  inherit them; explicit user values always win
- Strip the injected values on switch-away backfill (mirror-inverse of the
  injection conditions) so program defaults never harden into per-provider
  explicit values, and keep both keys out of the shared common-config snippet

src/config/claudeDesktopProviderPresets.ts

@@ -394,7 +394,7 @@ export const claudeDesktopProviderPresets: ClaudeDesktopProviderPreset[] = [
     apiFormat: "openai_responses",
     providerType: "codex_oauth",
     requiresOAuth: true,
-    modelRoutes: brandedRoutes("gpt-5.5", "gpt-5.5", "gpt-5.4-mini"),
+    modelRoutes: brandedRoutes("gpt-5.6", "gpt-5.6", "gpt-5.6-luna"),
     icon: "openai",
     iconColor: "#000000",
   },

src/config/claudeProviderPresets.ts

@@ -1227,10 +1227,32 @@ export const providerPresets: ProviderPreset[] = [
         // base_url 由代理后端强制重写为 chatgpt.com/backend-api/codex
         // 用户无需配置
         ANTHROPIC_BASE_URL: "https://chatgpt.com/backend-api/codex",
-        ANTHROPIC_MODEL: "gpt-5.5",
-        ANTHROPIC_DEFAULT_HAIKU_MODEL: "gpt-5.4-mini",
-        ANTHROPIC_DEFAULT_SONNET_MODEL: "gpt-5.5",
-        ANTHROPIC_DEFAULT_OPUS_MODEL: "gpt-5.5",
+        ANTHROPIC_MODEL: "gpt-5.6",
+        ANTHROPIC_DEFAULT_HAIKU_MODEL: "gpt-5.6-luna",
+        ANTHROPIC_DEFAULT_SONNET_MODEL: "gpt-5.6",
+        ANTHROPIC_DEFAULT_OPUS_MODEL: "gpt-5.6",
+        // Claude Code falls back to a 200K context window for unrecognized
+        // non-Claude model ids. The ChatGPT Codex backend catalogs gpt-5.6
+        // at a 372K window with a ~353K effective budget (openai/codex#31860),
+        // not the 1.05M API window. Declare 372K for both knobs: Claude Code's
+        // built-in output reserve and compact buffer already keep the compact
+        // trigger below the effective budget.
+        CLAUDE_CODE_MAX_CONTEXT_TOKENS: "${CLAUDE_CODE_MAX_CONTEXT_TOKENS}",
+        CLAUDE_CODE_AUTO_COMPACT_WINDOW: "${CLAUDE_CODE_AUTO_COMPACT_WINDOW}",
+      },
+    },
+    templateValues: {
+      CLAUDE_CODE_MAX_CONTEXT_TOKENS: {
+        label: "Max Context Tokens",
+        placeholder: "372000",
+        defaultValue: "372000",
+        editorValue: "372000",
+      },
+      CLAUDE_CODE_AUTO_COMPACT_WINDOW: {
+        label: "Auto Compact Window",
+        placeholder: "372000",
+        defaultValue: "372000",
+        editorValue: "372000",
       },
     },
     category: "third_party",

src/config/codexTemplates.ts

@@ -14,7 +14,7 @@ export interface CodexTemplate {
  */
 export function getCodexCustomTemplate(): CodexTemplate {
   const config = `model_provider = "custom"
-model = "gpt-5.5"
+model = "gpt-5.6"
 model_reasoning_effort = "high"
 disable_response_storage = true