docs: v0.8.0-alpha release notes — comment retention + gated-post sync

Re-stamped 0.8.0-alpha build carries the comment retention taxonomy fix
(only the anonymous/unsigned channel auto-expires; public and post-key-signed
comments are permanent; registry posts declare a flat 30-day policy) plus the
gated-post sync fix (posts rebuilt without their gating failed content-hash
verification and were silently discarded — this affected every bio carrying a
greeting slot). Upgrade note flags the unchanged Android version code.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LGiPD2cF75mnvneSCjdDC5

website/download.html

@@ -70,7 +70,14 @@
                 <li><strong>Preferred peers eliminated.</strong> The preferred tier existed to serve direct N+10 push/pull that the CDN's holder model replaced. Gone: the slot tier, the <code>preferred_peers</code> table, preferred-tree routing semantics, the rebalance priority pass, the relay candidate tiers, and the 7-day and 30-day watchers.</li>
             </ul>
 
-            <p style="color: var(--text-muted); font-size: 0.85rem;"><strong>Upgrade note:</strong> v0.8.0-alpha cannot talk to v0.7.x at all &mdash; that is intentional, and the anchor moves with this release. Existing data directories migrate in place on first run (manifest re-signing, legacy profile cleanup, registry materialization).</p>
+            <h3 style="margin-top: 1.25rem; font-size: 1rem;">Comment retention &mdash; corrected</h3>
+            <ul style="color: var(--text-muted); font-size: 0.85rem; line-height: 1.6; margin-top: 0.5rem;">
+                <li><strong>Only anonymous comments expire now.</strong> Retention is decided by the post's policy crossed with how the comment was signed. Public comments and comments from authorized (post-key-signed) commenters <em>never</em> auto-expire &mdash; an earlier build gave them a randomized 30&ndash;365 day lifetime, which would have deleted ordinary discussion on a timer. The randomized expiry now applies only to the private, unsigned channel strangers use, which is what retires throwaway conversation identities. Registry posts declare a flat 30-day policy binding every comment on them, so the directory self-cleans.</li>
+                <li><strong>Authors can cap or refuse anonymous comments per post</strong>, enforced by the nodes holding the post rather than trusted to the sender.</li>
+                <li><strong>Gated posts sync correctly.</strong> Several queries rebuilt posts without their gating metadata, so any gated post &mdash; including every bio carrying a greeting slot &mdash; failed its content-hash check at the receiver and was silently discarded. Greeting-enabled profiles now propagate as intended.</li>
+            </ul>
+
+            <p style="color: var(--text-muted); font-size: 0.85rem;"><strong>Upgrade note:</strong> v0.8.0-alpha cannot talk to v0.7.x at all &mdash; that is intentional, and the anchor moves with this release. Existing data directories migrate in place on first run (manifest re-signing, legacy profile cleanup, registry materialization). Android installs over an earlier 0.8.0-alpha may need an uninstall first, since the version code is unchanged.</p>
 
             <h2 style="margin-top: 2rem;">v0.7.3 &mdash; May 15, 2026</h2>
             <p style="color: var(--text-muted); font-size: 0.85rem;">Bandwidth + bootstrap hardening on top of v0.7.2. Wire-compatible with v0.7.0/v0.7.1/v0.7.2.</p>