Problem

When reading a Slack thread with slck messages thread <channel> <ts> --output text, long messages are truncated. Switching to --output json returns the full content.

This forces users to use JSON output and parse it themselves when they just want to read a thread — defeats the purpose of the human-friendly text format.

Reproduction

# Truncated output
slck messages thread CNGJGBL74 1774012357.028279 --output text

# Full output (same thread, complete content)
slck messages thread CNGJGBL74 1774012357.028279 --output json

Expected behavior

Text output should display the full message content, or at minimum offer a --no-truncate flag. If truncation is kept as a default for readability, it should be clearly indicated (e.g., [truncated] suffix).