Drop competitor framing from the marketing site

[rainxchzed]

Why

Earlier copy on the site framed F-Droid, Obtainium, and Aurora Store as competitors — comparison table on the homepage, "F-Droid alternative / Obtainium alternative" in meta + boilerplate, FAQ Q&A built around "How is GitHub Store different from X?". They aren't competitors of ours; the framing was unnecessary.

This PR strips that framing across the site. Factual integration mentions (F-Droid as an install channel, Obtainium import / export as a feature) stay — those describe what the app actually does and aren't competitive positioning.

Removed

• Homepage comparison table (full <section class="comparison"> block)
• Homepage FAQ entries: "How is GitHub Store different from F-Droid?", "How is GitHub Store different from Obtainium?"
• Same two Q&A entries from the FAQPage JSON-LD in _includes/head.html
• Homepage meta description: dropped "F-Droid + Obtainium alternative" → reads "Free, open-source app store for GitHub releases. Discover, install, and auto-update apps on Android, Linux, macOS, Windows. Silent install, China-friendly mirrors."
• Homepage meta keywords: dropped f-droid alternative, obtainium alternative
• Press kit boilerplate (3-paragraph version): removed the "Unlike F-Droid…" / "Unlike Obtainium…" sentences
• llms.txt: dropped "F-Droid + Obtainium alternative" from the summary line, dropped "comparison vs F-Droid / Obtainium / Aurora Store" from the homepage entry
• "comparison guides" content-type promise removed from blog hero, blog meta description, newsletter default subtitle, homepage Stay-in-the-loop subtitle, and the privacy policy newsletter usage clause

Replaced (FAQ parity stays at 5 entries, both visible HTML and JSON-LD)

• New: "Which platforms does GitHub Store support?" — Android / Windows / macOS / Linux + KMP/CMP one-liner
• New: "How does GitHub Store keep installs current?" — auto-update, Shizuku/Sui/Dhizuku, signing-fingerprint verification

Kept

• F-Droid + Obtainium as Android install methods on /download/. Distribution channel, factual.
• "Library Imports / Obtainium import / export" in /features/. Product feature, factual.

Cleanup not in this PR

• Dead .comparison* CSS rules in assets/css/site.css. Harmless leftover; sweep on a separate refactor PR if anyone wants to chase the byte count.

Misc

• Privacy policy bumped to v2.6 / Last Updated May 10, 2026 (the newsletter usage line changed wording).