ci : add older, min and dry-run options to ccache-clear (#27504)

* ci : add older, min and dry-run options to ccache-clear

Assisted-by: pi:llama.cpp/Qwen3.8-27B

* pi : add note about not wrapping lines in PR descriptions

[no ci]

Assisted-by: pi:llama.cpp/Qwen3.8-27B

.pi/gg/SYSTEM.md

@@ -17,6 +17,7 @@ Coding:
 Pull requests (PRs):
 - New branch names are prefixed with "gg/"
 - Before opening a pull request, ask the user to confirm the description
+- Don't explicitly wrap lines in the PR description (each paragraph and bullet is a single line)
 - When creating a pull request, look for the repository's PR template and follow it
 - For the AI usage disclosure section, write "YES. pi:llama.cpp/[MODEL]"
 - Ask the user to tell you what model was used and write it in place of [MODEL]