* fix(cli): measure and diff report why they failed, and reverse reports its runs
Since launch, 97 people saw a bare "Command failed" from measure: runMeasure
and diff called failCommand() without the error, so telemetry kept only the
wrapper. 59 agents ran `measure <file>` with no op and got no hint. Reverse
runs had no skill tag, so nobody could count how many finished.
- runMeasure and diff pass the error to failCommand.
- An unknown word that is an existing file names the commands to put first.
- references/start.md sends skill_invoked and skill_completed beacons.
* fix(cli): the file hint stays out of the root command list
Jerrai: `hyperframes index.html` would list every top-level command. fileHint moves to
didYouMean.ts, answers only inside a command group, and has tests for the root, a missing
file and a group with no commands.