feat(web): /install shell script + real curl one-liner on landing

Landing page showed \`curl -fsSL claudemesh.sh/install | bash\` but
the domain didn't resolve, so anyone copy-pasting got a DNS error.

Ship:
- apps/web/src/app/install/route.ts: GET returns an auditable bash
  installer (Node preflight, npm install -g claudemesh-cli, runs
  claudemesh install, prints next steps, colored output). No Node
  auto-install — fails clean if missing with a pointer.
- apps/web/src/proxy.ts: exclude /install from the i18n matcher so
  Next.js returns the shell script unmangled.
- hero.tsx + features.tsx: swap claudemesh.sh → claudemesh.com.

Test: curl http://localhost:3000/install | bash -n → OK.
Content-Type: text/x-shellscript; charset=utf-8.

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

apps/web/src/modules/marketing/home/features.tsx

@@ -45,7 +45,7 @@ export const Features = () => {
             style={{ fontFamily: "var(--cm-font-mono)" }}
           >
             <span className="text-[var(--cm-clay)]">$</span>
-            <span>curl -fsSL claudemesh.sh/install | bash</span>
+            <span>curl -fsSL claudemesh.com/install | bash</span>
             <button
               className="ml-2 rounded border border-[var(--cm-border)] px-1.5 py-0.5 text-[10px] text-[var(--cm-fg-tertiary)] transition-colors hover:border-[var(--cm-fg)] hover:text-[var(--cm-fg)]"
               aria-label="Copy"

apps/web/src/modules/marketing/home/hero.tsx

@@ -81,7 +81,7 @@ export const Hero = () => {
               style={{ fontFamily: "var(--cm-font-mono)" }}
             >
               <span className="text-[var(--cm-clay)]">$</span>
-              <span>curl -fsSL claudemesh.sh/install | bash</span>
+              <span>curl -fsSL claudemesh.com/install | bash</span>
             </div>
           </div>
         </Reveal>