fix: line up the columns in the two messages that offer a way out

[vyncint]

Both are first-run paths — what somebody reads when mossaic has just refused to do what they asked.

could not detect a GitHub user had one of its three suggestions two columns out of line, and listed --demo last. That is the only one of the three needing no account, no network and no decision, so it now comes second, right after charting someone by name.

  mossaic <username>  chart someone by name
  mossaic --demo      see what it looks like first
  gh auth login       authenticate, then just `mossaic`

The missing-file message is one I added earlier today, and it tried to align a column against an interpolated path — which cannot work, since the path is however long the reader typed. It also echoed the path back inside the suggestion, where it was noise. FILE says the shape of the command and lines up:

mossaic: no calendar file at /some/typo.json

  mossaic-art TEXT --snapshot FILE   write one
  mossaic --demo                     a sample year instead

Folded into the [0.6.3] changelog section, which is not tagged yet.

Checklist

• Tests added/updated — covered by tests/chart_cli.rs, which asserts the message names the file and offers both routes; 213 tests pass
• cargo fmt --all and cargo clippy --workspace --all-targets --all-features are clean
• All commits are signed off
• No AI attribution trailers
• CHANGELOG.md updated
• No snapshot changes