Add writing-clearly-and-concisely skill from tigris-blog (#1147)

Copy the Strunk-based writing skill that applies Elements of Style
rules to prose. Includes the SKILL.md and full elements-of-style.md
reference.

https://claude.ai/code/session_01VXpXouWGyQna6JLksukFup

Co-authored-by: Claude <noreply@anthropic.com>

Author: Xe

.claude/skills/writing-clearly-and-concisely/SKILL.md

@@ -0,0 +1,72 @@
+---
+name: writing-clearly-and-concisely
+description:
+  Apply Strunk's timeless writing rules to ANY prose humans will
+  read—documentation, commit messages, error messages, explanations, reports, or
+  UI text. Makes your writing clearer, stronger, and more professional.
+---
+
+# Writing Clearly and Concisely
+
+## Overview
+
+William Strunk Jr.'s _The Elements of Style_ (1918) teaches you to write clearly
+and cut ruthlessly.
+
+**WARNING:** `elements-of-style.md` consumes ~12,000 tokens. Read it only when
+writing or editing prose.
+
+## When to Use This Skill
+
+Use this skill whenever you write prose for humans:
+
+- Documentation, README files, technical explanations
+- Commit messages, pull request descriptions
+- Error messages, UI copy, help text, comments
+- Reports, summaries, or any explanation
+- Editing to improve clarity
+
+**If you're writing sentences for a human to read, use this skill.**
+
+## Limited Context Strategy
+
+When context is tight:
+
+1. Write your draft using judgment
+2. Dispatch a subagent with your draft and `elements-of-style.md`
+3. Have the subagent copyedit and return the revision
+
+## All Rules
+
+### Elementary Rules of Usage (Grammar/Punctuation)
+
+1. Form possessive singular by adding 's
+2. Use comma after each term in series except last
+3. Enclose parenthetic expressions between commas
+4. Comma before conjunction introducing co-ordinate clause
+5. Don't join independent clauses by comma
+6. Don't break sentences in two
+7. Participial phrase at beginning refers to grammatical subject
+
+### Elementary Principles of Composition
+
+8. One paragraph per topic
+9. Begin paragraph with topic sentence
+10. **Use active voice**
+11. **Put statements in positive form**
+12. **Use definite, specific, concrete language**
+13. **Omit needless words**
+14. Avoid succession of loose sentences
+15. Express co-ordinate ideas in similar form
+16. **Keep related words together**
+17. Keep to one tense in summaries
+18. **Place emphatic words at end of sentence**
+
+### Section V: Words and Expressions Commonly Misused
+
+Alphabetical reference for usage questions
+
+## Bottom Line
+
+Writing for humans? Read `elements-of-style.md` and apply the rules. Low on
+tokens? Dispatch a subagent to copyedit with the guide.