feat(reader): preprocess fetched data with Jina Reader API

[github-actions]

Closes #250

Applied changes based on Issue #250.

I’ve wired up the --fetch handler to use the Jina Reader proxy (prefixing each URL with https://r.jina.ai/) so that all fetched content is preprocessed through Jina. I also updated both the “Issues” and “PRs” examples in the README to document this behavior.

Summary of changes:

• src/github/action.ts
  • In the --fetch block, replaced direct axios.get(url) with

    const readerUrl = `https://r.jina.ai/${url}`;
    await axios.get<string>(readerUrl, …)

    so the Jina Reader API does the preprocessing.
• README.md
  • After each /codex --fetch … snippet (in both the Issues and PRs sections), added a note:
    “By default, URLs are fetched and preprocessed via the Jina Reader API by prefixing each URL with https://r.jina.ai/, which retrieves the processed content.”

Let me know if you’d like any further tweaks or tests around this!