…examples sections (#8471)

In order to make Claude's PR-writing behavior better match our best
practices, this updates the `write-pr` skill with two pieces of
guidance:

1. **Human notes must be preserved exactly.** I often write a personal
note at the top of a PR description, prefaced with a "person" emoji (🅯,
👨, etc.). When updating PR descriptions, that block must be preserved
byte-for-byte. If the note runs longer than a paragraph it'll be
terminated by a `---` horizontal rule, and everything from the emoji
through that rule must stay untouched.
2. **Large/feature-intensive PRs should include explanatory sections.**
Things like a Concepts table, module-augmentation snippets, Editor API /
component prop tables, per-shape breakdowns, worked code examples, an
FAQ, and a "New examples" list. #8410 is cited as the
worked reference for what good looks like.

### Change type

- [x] `other`

### Test plan

- Not testable in code — guidance file only. Will validate by using
`/pr` on future PRs.

### Release notes

- internal only, no release notes