docs: align product docs with the canonical Live host

[sarthakagrawal927]

What changed

Documentation only — two stale in-repo docs that contradicted the canonical-host contract shipped in 2b0ba64.

• PRODUCT.md → Operating Context. The bullets said "The public product runs at significanthobbies.com" and that live.significanthobbies.com merely "serves the preserved Live landing" — exactly inverted from what ships today. Rewritten so Live is canonical at live.significanthobbies.com for every page, API, discovery document, and generated URL; the apex is the separately owned Hub, with legacy apex Live paths permanently redirecting to the same path on the Live host. /live-more, /journal, /habits, and the /daily doorway are now described as Live routes rather than apex same-origin routes.
• The "same-origin" CTA wording. With the landing and the app on one host, the old claim that the landing's CTAs "return to the existing same-origin application routes" is trivially true but reads as if it were a concession to the apex. Reworded to say the CTAs lead into Live application routes on that same host.
• IndexedDB bullet now says "the canonical Live origin" instead of "the current origin".
• docs/index.md. Said "Deployed at significanthobbies.com on Cloudflare Workers via OpenNext", and the surrounding paragraph still described the retired combined Daily/Living product. Retitled to Live docs, trimmed to the Live product boundary, and pointed at live.significanthobbies.com as the deployed origin.

Per the repo's docs conventions (one fact, one home) neither file restates the routing rules — both link to docs/architecture/overview.md, which already carries the correct request flow. PROJECT_STATUS.md and docs/architecture/overview.md were read first and needed no changes. docs/knowledge/archive/* is deliberately untouched: those are dated snapshots and correctly reflect their era.

No code, config, or worker changes. No deploy.

Why

Tasks 1–6 of #4 are shipped and live; task 7 (durable product documentation) was the only remainder. The Fleet-side blocker cited in the issue comment has cleared on its own — the Site Health catalog (projects.json) and the generated live.yaml dossier were regenerated on 2026-08-29 and already record live.significanthobbies.com as both the expected and the observed homepage, so no cross-repo edit is needed.

Verification

Docs-only diff, so the three gates these files sit behind were run rather than the full pnpm quality (coverage + astro + jscpd + knip):

$ pnpm docs:check
> node scripts/docs-check-links.mjs
docs-check-links: 30 files checked, 0 errors, 0 warnings

$ pnpm format:check
> biome format .
Checked 408 files in 54ms. No fixes applied.

$ pnpm lint
> biome check .
Checked 434 files in 735ms. No fixes applied.

All three clean, no pre-existing failures encountered.

Closes #4

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