feat(stop-blathering): add skill

From the "be concise" section of ~/.codex/AGENTS.md (Grice's maxims),
citing Strunk's Elements of Style and Payne's Lively Art of Writing.

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

stop-blathering/SKILL.md

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+---
+name: stop-blathering
+description: >-
+  Stop blathering; be concise, truthful, relevant, clear (Grice's maxims) — use when writing or copy editing prose for a reader (docs, READMEs, skills, commit messages, PR descriptions, replies); when someone says "tighter", "too wordy", "blathering", "omit needless words", or cites Strunk & White or Grice; when about to say something you lack adequate evidence for. Optimize for reader attention: say what's needed, nothing the reader already knows, in an order easy to follow.
+---
+
+# Be concise; optimize for reader attention
+
+Take care to apply [Grice's four maxims](https://en.wikipedia.org/wiki/Cooperative_principle#Grice's_maxims)
+of conversation: quantity, quality, relation, and manner.
+
+The maxim of **quantity** is: be informative.
+
+Submaxims:
+
+- Make your contribution as informative as is required (for the current
+  purposes of the exchange).
+  **Do not make your contribution more informative than is required.**
+
+The maxim of **quality** is: be truthful.
+
+Supermaxim:
+
+- Try to make your contribution one that is true.
+
+Submaxims:
+
+- Do not say what you believe is false.
+- Do not say that for which you **lack adequate evidence**.
+
+The maxim of **relation** is: be relevant: the information provided
+should be relevant to the current exchange and omit any irrelevant
+information. Do not spend words on things the reader already knows.
+
+The maxim of **manner** is: be clear.
+
+Be brief — i.e., avoid unnecessary verbosity.
+Be orderly — i.e., provide information in an order that makes sense,
+and makes it easy for the recipient to process it.
+
+If you can say it with fewer words, do.
+
+## in practice
+
+- Link a well-known convention; don't restate it.
+- Cut tails that repeat a name, a link's target, or the obvious.
+- Quote the key line of a source; explain the rest in your own words.
+
+## sources
+
+- William Strunk Jr., [The Elements of Style](https://www.gutenberg.org/files/37134/37134-h/37134-h.htm)
+  (1918; later editions with E. B. White). Rule 13, "Omit needless words":
+
+  > Vigorous writing is concise. A sentence should contain no unnecessary
+  > words, a paragraph no unnecessary sentences, for the same reason that
+  > a drawing should have no unnecessary lines and a machine no
+  > unnecessary parts.
+
+- Lucile Vaughan Payne,
+  [The Lively Art of Writing](https://openlibrary.org/books/OL7410114M/The_Lively_Art_of_Writing)
+  (Prentice Hall, 1975; ISBN 978-0205091607)
+- [Cooperative principle — Wikipedia](https://en.wikipedia.org/wiki/Cooperative_principle)