fix(new-channels): prevent empty message send

[synoet]

No description provided.

[coderabbitai]

Caution

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Walkthrough

These changes add validation to prevent sending empty or whitespace-only messages. A new utility function hasSendableInputContent determines whether input has non-empty trimmed text or attachments. The send button now disables when there are pending attachments or insufficient sendable content. The send command gate checks for sendable content before proceeding with the send operation. Tests verify that whitespace-only messages return false without invoking callbacks, while messages with attachments return true regardless of text content.

Poem

🐰 Hoppy code hops along,
No empty words sent wrong—
Trim the space, check attachments too,
Send only when there's substance true! ✨

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 inconclusive)

Check name	Status	Explanation	Resolution
Description check	❓ Inconclusive	No pull request description was provided by the author, making it impossible to assess relevance to the changeset.	Add a pull request description explaining the rationale and implementation details of the empty message prevention feature.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and specifically summarizes the main change: preventing empty messages from being sent, which aligns with the changes across all modified files.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch synoet/new-channels-prevent-empty-message

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