privacy: remove external data transmissions & add GitHub release workflow

Remove three active external data transmission paths:

1. WebFetch domain blocklist (api.anthropic.com/api/web/domain_info)
   - src/tools/WebFetchTool/utils.ts
   - Was sending every domain a user tried to fetch to Anthropic
   - Replaced with always-allowed stub; tool permission dialog is
     the primary security boundary

2. Codex API router (chatgpt.com/backend-api/codex/responses)
   - src/services/api/codex-fetch-adapter.ts
   - Would have forwarded full conversation content to OpenAI
   - createCodexFetch now returns HTTP 403 stub

3. OpenAI API adapter (api.openai.com/v1/chat/completions)
   - src/utils/codex-fetch-adapter.ts
   - Would have forwarded messages to OpenAI
   - fetchCodexResponse now throws immediately

Already-disabled paths (no changes needed):
- Analytics logEvent/logEventAsync: empty stubs in services/analytics/index.ts
- GrowthBook/Statsig: local cache only, no outbound requests
- Auto-updater GCS: already guarded by CLAUDE_CODE_DISABLE_NONESSENTIAL_TRAFFIC
- MCP registry: already guarded by CLAUDE_CODE_DISABLE_NONESSENTIAL_TRAFFIC
- Release notes GitHub: already guarded by isEssentialTrafficOnly()

Add .github/workflows/release.yml:
- Builds self-contained binaries for macOS (x64+arm64), Linux (x64+arm64),
  Windows (x64) using bun compile on each native runner
- Triggers on version tags (v*.*.*) or manual workflow_dispatch
- Publishes binaries + SHA256SUMS.txt as a GitHub Release with
  per-platform install instructions

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/utils/codex-fetch-adapter.ts

@@ -83,53 +83,22 @@ function convertToOpenAIMessage(message: Message): OpenAIMessage {
 }
 
 /**
- * Make a request to OpenAI Codex API
+ * fetchCodexResponse is disabled: sending conversation content to
+ * api.openai.com would leak user data to a third-party service.
+ * This function is retained as a stub to avoid breaking any call sites.
  */
 export async function fetchCodexResponse(
-  messages: Message[],
-  model: string,
-  options: {
+  _messages: Message[],
+  _model: string,
+  _options: {
     apiKey?: string
     baseUrl?: string
     stream?: boolean
   } = {}
 ): Promise<OpenAIResponse> {
-  const { apiKey, baseUrl = 'https://api.openai.com/v1', stream = false } = options
-
-  if (!apiKey) {
-    throw new Error('OpenAI API key is required for Codex requests')
-  }
-
-  const openAIMessages = messages.map(convertToOpenAIMessage)
-
-  const requestBody = {
-    model,
-    messages: openAIMessages,
-    stream,
-    temperature: 0.7,
-    max_tokens: 4096,
-  }
-
-  try {
-    const response = await fetch(`${baseUrl}/chat/completions`, {
-      method: 'POST',
-      headers: {
-        'Content-Type': 'application/json',
-        'Authorization': `Bearer ${apiKey}`,
-      },
-      body: JSON.stringify(requestBody),
-    })
-
-    if (!response.ok) {
-      throw new Error(`OpenAI API error: ${response.status} ${response.statusText}`)
-    }
-
-    const data = await response.json() as OpenAIResponse
-    return data
-  } catch (error) {
-    logError(error)
-    throw error
-  }
+  throw new Error(
+    'OpenAI Codex API calls are disabled for privacy. External data forwarding has been removed.',
+  )
 }
 
 /**