v0.2.3 — public-readiness hardening + live demo

Added

• GitHub Pages live demo (xavi-999.github.io/metrognome) — the 3D Perf Map built from a real scan of bluesky-social/social-app at a pinned SHA (methodology example, clearly attributed) plus the sample-run report. Built by Actions; no generated HTML committed to main.
• CI: official plugin validation — claude plugin validate . --strict now runs in CI alongside the hand-rolled JSON checks.
• Community files — CONTRIBUTING.md (dev setup, test surface, critical contributor rules, release process), bug-report and feature-request issue forms, PR template.

Fixed

• marketplace.json was missing a top-level description — claude plugin validate . --strict failed; now passes.
• perf_scan.mjs printed a raw ERR_MODULE_NOT_FOUND stack when Babel deps were missing (silent SessionStart npm install failure) — now exits with one actionable remediation line.
• README: badges added (CI · release · license · live demo), intro paragraph tightened, live-demo links under the Perf Map screenshot, doctor:test alias in the scripts table.
• CLAUDE.md drift: playbook/doctor/smoke/test commands, heap_sample.mjs + build_playbook.mjs + templates/ci/ + workflows + docs/pages/ in the layout, .metrognome/playbook.md in the bootstrap list.
• Plugin metadata enriched: plugin.json ($schema, author email/url, Pages homepage, tightened description) and marketplace.json plugin entry (author, homepage, repository, license, keywords, category, tags).