Quality-improve 10 v7.0.0-era engineering skills

Applies three consistent fixes across the v7.0.0 batch:
- Rename `## Output Structure` → `## Output Format` for consistency
- Wrap output template in `---` document separators (code-review-checklist,
  debugging-log-analyser needed full structural upgrade; remaining 8 already
  had the wrapper)
- Remove `## Example Trigger Phrases` section from all 10 skills

Skills updated: code-review-checklist, debugging-log-analyser,
changelog-generator, pr-description-writer, system-design-interview,
test-strategy-doc, runbook-writer, incident-postmortem, api-docs-writer,
architecture-decision-record

Both `skills/` and `plugins/pm-engineering/skills/` copies synced.

https://claude.ai/code/session_01C3HwChrccJd145vJ6Z7ajF

skills/api-docs-writer/SKILL.md

@@ -16,7 +16,7 @@ Ask the user for these if not provided:
 - **Audience** (internal developers / external partners / public)
 - **Output format** (Markdown / OpenAPI YAML / Plain prose)
 
-## Output Structure
+## Output Format
 
 For each endpoint, produce the following:
 
@@ -137,10 +137,3 @@ data = response.json()
 - [ ] Auth method is clearly stated at the top
 - [ ] Enum values are listed where applicable
 - [ ] Pagination documented if the endpoint is a list endpoint
-
-## Example Trigger Phrases
-
-- "Document this API endpoint: [paste spec or description]"
-- "Turn this Postman collection into developer docs"
-- "Write API reference docs for [endpoint]"
-- "Write a developer guide for our [product] API"