[AIAA] Build step 3: assessment request intake form

Build step 3 of the AI-assisted assessment system: the intake form.

Deliverable: `.github/ISSUE_TEMPLATE/assessment-request.yml`. A request
collects the project's basics (name, maturity, website, docs site,
repository, scope), the documentation domains that seed the firewall
allowlist at acceptance, and the project contacts. The form states up
front that assessments are AI-drafted and human-reviewed, and a
required checkbox acknowledges it. Filing does not start an
assessment: a technical writer triages and accepts.

Applies labels `Docs analysis` and `needs-triage` at filing.

Ordering note: `needs-triage` lands with the step 1 PR. A dry-run
filed before that merges will silently drop the label, so the dry-run
happens after both PRs are in.

Done when a dry-run request files cleanly with all fields collected.

- [ ] Draft verified locally (assertion script green, `npm run check`
passes)
- [ ] PR opened
- [ ] Step 1 PR merged (label dependency)
- [ ] Dry-run request filed cleanly, then closed
- [ ] Merged