feat(ide): add GEMINI_CLI_IDE_PID env var to override IDE process detection (#15842)

Co-authored-by: Adib234 <30782825+Adib234@users.noreply.github.com>

docs/ide-integration/index.md

@@ -170,6 +170,20 @@ messages and how to resolve them.
   - **Solution:** Run `/ide enable` to try and reconnect. If the issue
     continues, open a new terminal window or restart your IDE.
 
+### Manual PID override
+
+If automatic IDE detection fails, or if you are running Gemini CLI in a
+standalone terminal and want to manually associate it with a specific IDE
+instance, you can set the `GEMINI_CLI_IDE_PID` environment variable to the
+process ID (PID) of your IDE.
+
+```bash
+export GEMINI_CLI_IDE_PID=12345
+```
+
+When this variable is set, Gemini CLI will skip automatic detection and attempt
+to connect using the provided PID.
+
 ### Configuration errors
 
 - **Message:**