fix: align Masker site metadata and public claims

[kiku-jw]

Summary

• add the GitHub Pages canonical URL and a precise description
• label the browser demo as a narrow client-side regex preview
• remove unsupported privacy, latency, F1, accuracy, and Luhn-validation claims
• render pasted text through text nodes instead of innerHTML while preserving masked highlights
• align package and contribution metadata with the repository's existing AGPL-3.0 license
• remove the unsupported Production/Stable classifier

Surface and scope

Surface: pages-product
Verdict: site-baseline

The API runtime and detection behavior are unchanged. The Pages demo now describes only the three regex patterns it actually runs. This intentionally adds no schema, sitemap, FAQ, new dependency, benchmark, or broader security/accuracy claim.

Verification

• demo JavaScript syntax — passed
• hostile pasted-markup DOM test — passed; user text creates no DOM nodes
• HTML semantics, canonical, description, and link checks — passed
• Python/JSON syntax and source/OpenAPI description parity — passed
• RapidAPI YAML syntax — passed
• repo-wide unsupported-claim and stale-license scans — passed
• git diff --check origin/main...HEAD — passed
• secret-pattern scan — no matches
• independent review — approved

The full pytest collection was not run locally because spacy is absent; no dependency was installed. Existing GitHub CI remains the authoritative full test gate.

License impact: metadata is aligned to the existing root AGPL-3.0 license; this is not a relicensing.
Branch-protection impact: none.
Secrets check: no real secrets added.

Tracks kiku-jw/kikuai-project-map#13.