#8842: feat: add sparkly new tagline

Adds a new tagline to the CLI rotation: "Keeping your shell shiny and your claws sharp." AI-Assisted - [x] Mark as AI-assisted - Degree of testing: Lightly tested (string addition) - Confirmed understanding: Yes, just adding a string to the `TAGLINES` array. <!-- greptile_comment --> <h2>Greptile Overview</h2> <h3>Greptile Summary</h3> This PR adds a new non-holiday tagline ("Keeping your shell shiny and your claws sharp.") to the CLI’s `TAGLINES` rotation in `src/cli/tagline.ts`. The rest of the diff is a formatting-only change (indentation) to a few helper functions that build `HolidayRule` predicates; runtime behavior should remain unchanged. <h3>Confidence Score: 5/5</h3> - This PR is safe to merge with minimal risk. - Change is limited to adding a single string literal to the `TAGLINES` array; the additional diff appears to be indentation/formatting only and does not alter logic. - No files require special attention <!-- greptile_other_comments_section --> _{(2/5) Greptile learns from your feedback when you react with thumbs up/down!} <!-- /greptile_comment -->