chore(release): fix README command count + point dialog at v0.20.0 notes

- apps/hook/README.md: 'four' -> 'three' slash commands (archive row was
  removed in #873 but the count wasn't reverted).
- LookAndFeelAnnouncementDialog: 'Full release notes' now deep-links to the
  v0.20.0 release tag instead of the generic releases list.

apps/hook/README.md

@@ -106,7 +106,7 @@ Host your-server
 
 ## Slash Commands
 
-Plannotator's slash commands are installed as Claude Code skills in `~/.claude/skills` by the install script (the canonical source is `apps/skills/core/`). Claude Code skills are user-invocable by directory name, so these four work like slash commands inside your session:
+Plannotator's slash commands are installed as Claude Code skills in `~/.claude/skills` by the install script (the canonical source is `apps/skills/core/`). Claude Code skills are user-invocable by directory name, so these three work like slash commands inside your session:
 
 | Command | Description |
 |---------|-------------|

packages/ui/components/LookAndFeelAnnouncementDialog.tsx

@@ -79,7 +79,7 @@ export const LookAndFeelAnnouncementDialog: React.FC<LookAndFeelAnnouncementDial
               <div className="flex items-start justify-between gap-4">
                 <h3 className="font-semibold text-2xl mb-1.5">Plannotator 0.20.0 is here</h3>
                 <a
-                  href="https://github.com/backnotprop/plannotator/releases"
+                  href="https://github.com/backnotprop/plannotator/releases/tag/v0.20.0"
                   target="_blank"
                   rel="noopener noreferrer"
                   className="shrink-0 mt-1.5 text-xs font-medium text-muted-foreground hover:text-foreground transition-colors"