fix: address critical/high audit findings across WASM sub-crates

- Telegram: remove .unwrap() panic on workspace_read (owner_id check)
- WhatsApp: use configured api_version instead of hardcoded v18.0
- WhatsApp: log config parse errors before falling back to defaults
- Slack: log serialization errors in emit_message and json_response
- Google Docs: safe array access for batch update replies
- Google Sheets: safe array access for add_sheet replies
- Google Calendar: fix doc comment secret name mismatch
- Gmail: avoid unnecessary String allocation in UNREAD check

Co-Authored-By: Claude Opus 4.6 <[email protected]>

tools-src/google-sheets/src/api.rs

@@ -330,7 +330,13 @@ pub fn add_sheet(spreadsheet_id: &str, title: &str) -> Result<AddSheetResult, St
 
     let parsed = batch_update(spreadsheet_id, requests)?;
 
-    let reply = &parsed["replies"][0]["addSheet"]["properties"];
+    let reply = parsed["replies"]
+        .as_array()
+        .and_then(|arr| arr.first())
+        .map(|r| &r["addSheet"]["properties"]);
+
+    let reply = reply.ok_or("No reply from batch update")?;
+
     Ok(AddSheetResult {
         sheet: SheetInfo {
             sheet_id: reply["sheetId"].as_i64().unwrap_or(0),