fix(web): start CTAs → /auth/register + GitHub link → claude-intercom OSS

All conversion CTAs were pointing to the dead github.com/claudemesh/
claudemesh repo or # hash fragments. Landing is the primary funnel for
v0.1.0 — every "Start" button is a conversion-critical surface.

Fixes:
- Header "Start free" → /auth/register
- Header GitHub nav item → REMOVED (kept the icon button, repointed)
- Hero "Start free" → /auth/register
- Pricing 6× CTAs: Solo/Pro/Plus/Team/Business → /auth/register,
  Enterprise → /contact
- CTA footer "Star on GitHub" → /auth/register ("Start free")
- BeyondTerminal "Read the protocol spec" → /auth/register
  ("Get on the mesh")

GitHub reinstated as a dedicated icon button in the header right side,
pointing to https://github.com/alezmad/claude-intercom — the MIT OSS
foundation claudemesh is built on. Honest provenance: claude-intercom
is the local peer-mesh gift to the community, claudemesh is the hosted
cross-machine extension.

Tooltip: "Built on claude-intercom · MIT open source".

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/web/src/modules/marketing/home/beyond-terminal.tsx

@@ -219,12 +219,11 @@ export const BeyondTerminal = () => {
             <span className="text-[var(--cm-fg-secondary)]">anything</span>
           </p>
           <Link
-            href="https://github.com/claudemesh/claudemesh#protocol"
-            target="_blank"
+            href="/auth/register"
             className="inline-flex items-center gap-2 rounded-[var(--cm-radius-xs)] border border-[var(--cm-fg-tertiary)] px-5 py-2.5 text-sm font-medium text-[var(--cm-fg)] transition-colors hover:border-[var(--cm-fg)] hover:bg-[var(--cm-bg-elevated)]"
             style={{ fontFamily: "var(--cm-font-sans)" }}
           >
-            Read the protocol spec →
+            Get on the mesh →
           </Link>
         </Reveal>
       </div>