fix(ai): use "(no tool output)" placeholder for empty tool results without images (#6290)

OpenAI Completions and Responses providers unconditionally replaced empty
tool result text with "(see attached image)", even when the result had no
image content. This caused the model to hallucinate image attachments for
commands that produce no output (e.g. curl -s with SSL errors, grep with
no matches, true/false).

Now matches the Google provider behavior: "(see attached image)" is only
used when images are actually present; empty results get "(no tool output)".

Co-authored-by: tzwm <tzwm@users.noreply.github.com>
Co-authored-by: Mario Zechner <badlogicgames@gmail.com>

packages/ai/CHANGELOG.md

@@ -11,6 +11,7 @@
 - Fixed Amazon Bedrock prompt-cache points for Claude Fable 5 and Claude Sonnet 5 ([#6235](https://github.com/earendil-works/pi/issues/6235)).
 - Fixed DS4 server context overflow detection for `Prompt has ... tokens, but the configured context size is ... tokens` errors ([#6262](https://github.com/earendil-works/pi/issues/6262)).
 - Fixed OpenAI Codex WebSocket sessions to rotate cached connections before the backend's 60-minute limit, avoiding connection-limit failures on long sessions ([#6268](https://github.com/earendil-works/pi/issues/6268)).
+- Fixed OpenAI Completions and Responses providers to send `(no tool output)` instead of `(see attached image)` when a tool result has empty text and no image content, preventing the model from hallucinating image attachments.
 - Fixed OpenAI Responses and Azure OpenAI Responses requests to avoid sending `max_output_tokens` values below the provider minimum ([#6265](https://github.com/earendil-works/pi/issues/6265)).
 - Fixed retry classification for Cloudflare 524 timeout responses ([#6239](https://github.com/earendil-works/pi/issues/6239)).