feat: streaming draft responses via sendMessageDraft

[Fr4nzz]

Summary

• Rewrite DraftStreamer to support both sendMessageDraft (private chats) and editMessageText (group chat fallback)
• Add cursor ▌ during streaming for visual typing feedback (like OpenClaw)
• Minimum 20 chars before first draft send (avoids triggering push notifications with fragments)
• Anti-regressive updates: skip edits where text got shorter
• Smart error classification: distinguish draft-unavailable, message-not-modified, message-deleted
• Self-disabling after 3 consecutive errors
• Add ENABLE_STREAM_DRAFTS and STREAM_DRAFT_INTERVAL config options
• Support verbose level 3 (full command output)

Test plan

• Enable ENABLE_STREAM_DRAFTS=true and send a text prompt
• Verify response text streams token-by-token with cursor ▌
• Verify cursor disappears when response is finalized
• Test in group chat: should fall back to editMessageText
• Verify no draft sent before 20 characters accumulated

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