proper fix for image attachments

[shuv1337]

When reading text files via ReadTool, append any returned attachments (e.g., images) as synthetic file parts; otherwise fall back to the original file part.

• Session handling (packages/opencode/src/session/prompt.ts):
  • ReadTool file handling:
    • After executing ReadTool for text/plain file inputs, push the text output and then:
      • If result.attachments exist, append them as synthetic file parts with filename defaulted to the original part’s filename.
      • Otherwise, append the original file part.
    • Ensures attachments (e.g., images) from tools are correctly attached to the message.

[shuv1337]

@rekram1-node 🙏

[rekram1-node]

sorry for delay SO busy lately