rename stop-blathering to grice-maxims

A civil name for the same skill; "stop blathering" stays a trigger
phrase in the description, which now leads with replies: they happen
every turn, so they never look like a task that calls for a skill.
The README gloss now covers all four maxims, not just brevity.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

README.md

@@ -36,7 +36,8 @@ Code](https://code.claude.com/docs/en/skills) and
 
 ## writing prose
 
-- [stop-blathering](stop-blathering/SKILL.md) — omit needless words.
+- [grice-maxims](grice-maxims/SKILL.md) — say what's needed and no
+  more, only what you can back up, in an order easy to follow.
 - [hypertext-links](hypertext-links/SKILL.md) — link text says where
   the link goes; no bare URLs, no "click here".
 - [citation-needed](citation-needed/SKILL.md) — back a challenged claim