Fix message disappearing when queued during task execution

[roomote]

Fixes issue where messages disappear when sent while Roo is busy.

Changes:

• Add null check for getCurrentTask() in queueMessage handler
• Handle edge case where task finishes just as message is queued
• Preserve user's message if queuing fails

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View task on Roo Code Cloud

[roomote]

Rooviewer   See task on Roo Cloud

I reviewed this PR and found no issues. The implementation correctly handles the edge case where a task ends between when the user clicks send and when the queued message is processed.

Changes look good:

• Adds null check for getCurrentTask() in the queueMessage handler
• Sends queueMessageFailed message to restore user input when queueing fails
• Properly handles the message in ChatView to restore text and images
• Type union updated correctly in ExtensionMessage.ts

_{Mention @roomote in a comment to request specific changes to this pull request or fix all unresolved issues.}