Concise transcript "N commands" groups render full untruncated command text when collapsed #5427

Describe the bug

Version: Copilot CLI 1.0.110-1 (prerelease channel), macOS darwin-arm64
Flag: CONCISE_TRANSCRIPT enabled by rollout

Expected: A collapsed group takes about one line, like the pre-concise "Shell " row: a command-count header plus at most a one-line truncated preview. This matches the 1.0.108 changelog: "Keep successful command output and file diffs collapsed in concise transcript mode until expanded."

Actual: The collapsed group prints the entire command, wrapped. One heredoc fills most of the screen. The command description isn't shown either.

Cause (1.0.110-1 cli-main.js, minified):

• The collapsed preview (X5i) renders e.command with wrap:"wrap", with no first-line limit or truncation.
• The preview picker (eqi) always previews a 1-operation group, even after it succeeds (...??(n?.type==="focused_command"?n:void 0)). It also previews the running command, failed commands, and the last command of the trailing ("settling") group while the turn is active. So every single-command group, and every in-flight group, shows its full command text.

Suggested fix: truncate the collapsed preview to the first line (truncate-end), prefer the command's description when one exists, and/or don't preview completed single-command groups.

Workaround: enabledFeatureFlags.CONCISE_TRANSCRIPT=false in settings.json, which also removes the grouping.

Affected version

1.0.110-1

Steps to reproduce the behavior

1. With CONCISE_TRANSCRIPT on, have the agent run a long shell command, such as
   a python3 heredoc of about 50 lines.
2. Look at the timeline without expanding anything.

Expected behavior

A collapsed group takes about one line, like the pre-concise "Shell " row: a command-count header plus at most a one-line truncated preview. This matches the 1.0.108 changelog: "Keep successful command output and file diffs collapsed in concise transcript mode until expanded."

Additional context

No response