fix(website): simplify downloads and scope product releases (#390)

## Problem and outcome

Website visitors can download the usual Windows x64, macOS Apple silicon
and Linux x64 App packages directly from clearly labeled platform cards.
Each card includes a verified Gitee alternative, with shared setup
guidance and a More downloads link for the full release list. The
homepage reuses the application's 20 bilingual greetings, and the sample
game no longer displays an invented title.

Website builds resolve links from the latest published GitHub release
and validate matching mirror assets. Website deployment follows main CI
so newly published packages reach the next site build. Version selection
and release notes now share a product-change filter: standalone website,
documentation and maintenance changes do not create App/Server releases
or affect the next product version.

## Verification

- `npm run check`: 57 test files / 759 tests, TypeScript and product
production build passed.
- Website build passed with real GitHub/Gitee v1.0.0 metadata and with
the explicit local fallback.
- English and Chinese browser checks at 390px and 1440px passed:
platform links, More downloads, greeting selection and language
switching.
- All 23 website film check groups passed; the final shared artwork
change rebuilt successfully.
- Documentation, repository hygiene and diff checks passed. Real
Git-history tests cover product/website mixtures and moves across the
release boundary; the accepted phase plans `publish: false`.

## Impact

GitHub remains the version authority; Gitee is a download mirror.
Unavailable mirror metadata falls back to its release page. Product
runtime behavior and package compatibility are unchanged. Physical
macOS/Linux capture and broader device/network limits remain documented.

docs/operations/github.md

@@ -30,9 +30,11 @@ copy and repository visibility; finish main protection. Then set repository
 Actions variable `PIIK_RELEASES_ENABLED` to `true`. This is a repository setting,
 not an environment variable for Piik App or Server.
 
-Subsequent accepted PRs merged to main use the existing CI workflow: calculate
-one version, validate, package Server and all App targets, and publish the same
-artifacts. Runs queue rather than overlap or cancel one another. Branches/PRs
+Subsequent accepted PRs merged to main use the existing CI workflow. Product
+changes calculate one version, validate, package Server and all App targets,
+and publish the same artifacts. Standalone website/docs changes validate without
+packaging or releasing; [versioning](../reference/versioning.md#automatic-publication)
+owns that boundary. Runs queue rather than overlap or cancel one another. Branches/PRs
 stay quiet; manual `client_checks` dispatch remains available for candidates.
 Writing a new version back to main is unnecessary and prohibited.
 
@@ -84,8 +86,8 @@ Use the release's actual version and full `target_commitish` SHA, with
 `GITEE_TOKEN` supplied through the publisher environment. `--dry-run` after the
 three arguments checks local identity, checksums and attachment sizes without
 publishing. The [release-source policy](../reference/versioning.md#release-sources)
-owns provenance, selection and quota limits. Small-file upload/download acceptance
-has passed; full-package mirror acceptance remains part of release readiness.
+owns provenance, selection and quota limits. The first public release passed
+complete matching Server and three-platform App mirror download acceptance.
 
 ## Platform References