--reply-to fails with thread IDs (only accepts message IDs)

[willtmc]

Bug

The --reply-to flag fails when given a thread ID (which is what gmcli search returns). It only works with message IDs.

Steps to reproduce

# Search returns thread IDs
gmcli user@example.com search "in:inbox" --max 1
# Returns: 19b18de0c8734107 (thread ID)

# Using that thread ID with --reply-to fails
gmcli user@example.com drafts create \
  --to "someone@example.com" \
  --subject "Re: Test" \
  --body "Reply text" \
  --reply-to "19b18de0c8734107"
# Error: Requested entity was not found.

# But using the message ID works
gmcli user@example.com thread 19b18de0c8734107
# Shows Message-ID: 19b18fc8d2776818

gmcli user@example.com drafts create \
  --to "someone@example.com" \
  --subject "Re: Test" \
  --body "Reply text" \
  --reply-to "19b18fc8d2776818"
# Draft created: r1234567890

Expected behavior

--reply-to should accept either a thread ID or message ID, since the CLI primarily works with thread IDs.

Suggested fix

In gmail-service.js, detect if the ID is a thread ID and fetch the last message from that thread:

// If replying to a specific message, fetch its headers
if (options.replyToMessageId) {
    let messageIdToFetch = options.replyToMessageId;
    try {
        await gmail.users.messages.get({
            userId: "me",
            id: messageIdToFetch,
            format: "minimal",
        });
    } catch (e) {
        // Probably a thread ID - get the thread and use the last message
        const thread = await gmail.users.threads.get({
            userId: "me",
            id: options.replyToMessageId,
            format: "minimal",
        });
        if (thread.data.messages && thread.data.messages.length > 0) {
            messageIdToFetch = thread.data.messages[thread.data.messages.length - 1].id;
        }
    }
    const msg = await gmail.users.messages.get({
        userId: "me",
        id: messageIdToFetch,
        format: "metadata",
        metadataHeaders: ["Message-ID", "References"],
    });
    // ... rest of the code
}

This needs to be applied in both createDraft and sendMessage functions.

I've tested this patch locally and it works for both thread IDs and message IDs.

[willtmc]

Hey Mario - I've been using gmcli heavily and really appreciate you building this. It's become a key part of my workflow.

Since I need these fixes for day-to-day use, I'm going to maintain a fork at willtmc/gmcli with the patches applied.

Happy to submit a PR if you'd prefer to merge upstream instead - just let me know. Thanks for the great tool!