feat(web): add basic SEO and link zycode to the repo and PyPI - #54

Summary

 web/src/layouts/Base.astro                (the <head> of each page)
+  <link rel="icon" href="/favicon.ico" sizes="32x32">
+  <link rel="apple-touch-icon" href="/apple-touch-icon.png">
+  <meta name="twitter:site" content="@zycodey1">         from links.x in data/site.ts
+  <meta name="twitter:image:alt" ...>
+  <script type="application/ld+json">                    home pages only; no data on a preview address
+    WebSite              name, alternateName, url, inLanguage
+    SoftwareSourceCode   codeRepository, license, programmingLanguage, keywords, sameAs
 web/public/
+  favicon.ico             16, 32, 48 px
+  apple-touch-icon.png    180 x 180 px
 README.md, packages/pi-agent-cli/README.md
+  "zycode is an open-source coding agent ... Website: zycode.dev"
 pyproject.toml            (root and 6 packages)
+  [project.urls] Website = "https://zycode.dev"
 web/README.md
+  ## Icons
+  ## Search engines       rules for the JSON-LD: sourced values only, no rating, no review

Evidence

• Before: https://zycode.dev/favicon.ico and /apple-touch-icon.png return 404. The word "zycode" is
  not in README.md, not in the PyPI pages, and the GitHub About text is "pi-agent for python" with no website.
  After: both icons return 200 (image/x-icon, image/png), and each page has one JSON-LD block.

• Built pages (dist/index.html, dist/zh/index.html, dist/404.html), checked by a script:
  the JSON-LD is valid JSON with 2 nodes; no aggregateRating, no review; no raw < in it; one <h1>;
  twitter:site is @zycodey1; the canonical link is on zycode.dev; 404.html has noindex and no JSON-LD.

• Each of the 14 JSON-LD properties is a property of its type in the schema.org vocabulary (release 30.1):
  a script read the vocabulary file and followed domainIncludes through the parent types.

• The icons match favicon.svg: Edge draws the SVG at 256 px; mean difference to favicon.ico art
  is 0.3 of 255, and 1 pixel of 65,536 differs by more than 48.

• In a browser (npm run preview): the page shows as before, and fetch of the 3 icons gives 200.

• npm run check: 0 errors. npm run build: 3 pages. ruff check . and ruff format --check .: pass.
  scripts/tests/test_release_versions.py: 4 passed. uv build --wheel for the root package and for
  pi-agent-cli-lc: the wheel metadata has Project-URL: Website, https://zycode.dev.

• Not tested: Google Rich Results Test and Search Console (the page is not public before the merge, and
  Google and schema.org do not answer from my network); PageSpeed; how a search engine shows the site after a crawl.

• Outside this pull request: I set the GitHub About text, the website, and 10 topics of the repository.
  I opened agentclientprotocol/agent-client-protocol#2681,
  which adds zycode to the agents list of the ACP site.

Merge Danger

Door: two-way. Revert the commit to go back.

A merge changes web/, so Cloudflare Workers Builds deploys zycode.dev by itself (about one minute).
The change adds head tags and two static files. The body of the pages does not change.

Blast Radius: the <head> of / and /zh/ (search engines, link previews, the tab icon), and the PyPI
metadata of 7 packages. The PyPI pages change only after the next release.