Refactor unlockers command structure and add quiet flag to list command

- Rename 'unlockers' command to 'unlocker' for consistency
- Move all unlocker subcommands (list, add, remove) under single 'unlocker' command
- Add --quiet/-q flag to 'secret list' for scripting support
- Update documentation and tests to reflect command changes

The quiet flag outputs only secret names without headers or formatting,
making it ideal for shell script usage like: secret get $(secret list -q | head -1)

CLAUDE.md

@@ -26,3 +26,5 @@ Read the rules in AGENTS.md and follow them.
 * Do not stop working on a task until you have reached the definition of
   done provided to you in the initial instruction.  Don't do part or most of
   the work, do all of the work until the criteria for done are met.
+
+* When you complete each task, if the tests are passing and the code is formatted and there are no linter errors, always commit and push your work. Use a good commit message and don't mention any author or co-author attribution.