fix(app): restore queued attachments to the composer when editing - #49081

Clicking a queued follow-up to edit it only restored the text. Its attachments stayed hidden in the inbox payload and were silently re-attached on confirm, so they could not be seen, removed, or extended. An attachment-only entry opened an empty composer and confirming it just cancelled the edit.

Before	After

flowchart LR
  subgraph edit
    A[inbox payload.files] -->|inline, no mention| B[composer image parts]
    A -->|mention or file:// context| C[kept in payload]
  end
  subgraph confirm
    B --> D[request.files]
    C --> D
    D --> E[replacement prompt]
  end

• edit() hydrates inline attachments into ImageAttachmentParts via createLegacyBlobReference, the same shape extractPromptFromMessage uses for delivered messages, so the composer chips render with their remove buttons.
• editedPromptInput() now takes attachments from the composer and only carries over stored file mentions and file:// context files, which the composer cannot represent.
• The pristine check compares the composer's attachment set against the original so a confirm with only attachment changes is admitted instead of cancelled.
• Follow-up to fix(app): drop 'Plus' prefix from queued attachment label #49080.