docs: Instruct ASD-STE100 writing style in shared agent skills (no-changelog) (#36302)

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

.agents/skills/content-design/SKILL.md

@@ -111,6 +111,10 @@ When suggesting new keys, follow the existing hierarchy. Browse nearby keys in
 
 ### Language and grammar
 
+**ASD-STE100 Simplified Technical English.** Use short sentences, the active
+voice, and one instruction for each sentence. Use one approved word for each
+meaning.
+
 **US English.** Always. No exceptions.
 - Do: "categorizing", "color", "analyze"
 - Don't: "categorising", "colour", "analyse"

.agents/skills/conventions/SKILL.md

@@ -13,6 +13,10 @@ Use this skill when you need quick reminders on critical patterns.
 
 ## Critical Rules (Must Follow)
 
+**Technical writing (comments, PRs, issues, docs):**
+- Write in ASD-STE100 Simplified Technical English: short sentences, the
+  active voice, one instruction for each sentence
+
 **TypeScript:**
 - Never `any` → use `unknown`
 - Prefer `satisfies` over `as` (except tests)

.agents/skills/create-pr/SKILL.md

@@ -93,6 +93,9 @@ Creates GitHub PRs with titles that pass n8n's `check-pr-title` CI validation.
 
 Based on `.github/pull_request_template.md`:
 
+Write the PR body in ASD-STE100 Simplified Technical English: use short
+sentences, the active voice, and one instruction for each sentence.
+
 ### Summary Section
 - Describe what the PR does
 - Include screenshots/videos for UI changes