docs(readme): local preview, prerequisites, owner-wording fix, polish

[mikim]

README-only polish. The README was already accurate (an adversarial review found 0 factual errors and 0 broken links across every claim — field lists, the 12-tier enum, the 7 chips, section names, all commands, both CI workflows, precedence subtleties). These changes close a few first-time-reader gaps and one wording inaccuracy, without touching its verified-accurate style. Every new claim was checked against the repo.

Substantive (recommended)

1. Local preview — the README gave the generate + validate commands but never said how to view the rendered page, which is the whole product. Added a one-liner. Grounded: the generated index.html has 0 runtime fetches and inlined CSS, so open index.html works over file://.
2. Prerequisites — no toolchain/versions were stated. Added them, grounded in what CI actually pins: Node 22 and Python 3.12 (.github/workflows/registry.yml lines 23/28); there is no package.json/.nvmrc, so CI was the only source. Also cross-referenced the pip install "jsonschema[format-nongpl]" prereq at the contributor walkthrough's validate step (it appeared only once before, so a reader following steps 1–6 could hit ModuleNotFoundError).
3. Accuracy fix — the Files table described adoption.yaml as recording a "named human owner"; the human_owner is a maintainers body (MosslandOpenDevs maintainers), which the adoption file itself distinguishes from "a single named individual." Reworded to "the human owner (a named maintainers body)".
4. Onboarding — a top-of-file "Contributing?" pointer to AGENTS.md + the add-a-service section (previously only in the Files table and a buried blockquote).

Stylistic (easy to drop if you'd rather not)

5. Contents table (the doc is ~190 lines / 8 sections).
6. CI badges — registry.yml + assurance.yml. They visualize the README's central "CI enforces this" claim; drop them if you prefer the badge-free look.
7. Nits — descriptive H1 (Mossland Verified Links instead of the repo slug); gloss 최종 확인 as "(last-verified)" to match the KR/EN pairing used everywhere else; fix a comma splice ("this, it is" → "this — it is").

Verification

• All in-page anchors and file links resolve — 0 broken (checked every #anchor against the heading slugs and every relative link with test -e; badge workflow files exist).
• README-only: no functional/site code, no generated file, no assurance artifact changed. The v0.5.0 adopter check stays exit 0 / 0 ERROR-WARN (README is not a validated artifact), and the drift gate sees no adoption/register change.

Review

Do not merge without owner review. Docs-only; nothing here is decided by the drafting agent. The substantive items (1–4) and stylistic items (5–7) are separated above so you can cherry-pick during review.