feat: add reciprocal Deep dives blog link blocks to the warmup, sending, and deliverability pillar pages so clusters link both directions

site/src/pages/deliverability.astro

@@ -3,6 +3,7 @@ import Layout from '../layouts/Layout.astro';
 import HeroAtmosphere from '../components/HeroAtmosphere.astro';
 import Icon from '../components/Icon.astro';
 import CTA from '../components/CTA.astro';
+import PillarPosts from '../components/PillarPosts.astro';
 
 // Every number on this page is a real default from the codebase:
 //   internal/config/constants.go
@@ -856,6 +857,15 @@ const numbers = [
     </div>
   </section>
 
+  <PillarPosts
+    title="Deliverability, in more depth"
+    items={[
+      { kicker: 'Authentication', href: '/blog/spf-dkim-dmarc-alignment-cold-email/', title: 'SPF, DKIM, DMARC alignment: why your green checkmarks can lie' },
+      { kicker: 'Metrics', href: '/blog/delivery-rate-is-not-inbox-placement/', title: 'Delivery rate is not inbox placement' },
+      { kicker: 'Thresholds', href: '/blog/complaint-rate-that-gets-you-throttled/', title: 'What complaint, bounce, and spam rate gets you throttled?' },
+    ]}
+  />
+
   <CTA
     title="See where your mailbox really stands."
     description="Connect one and get a full SPF, DKIM, DMARC, and PTR report, plus its current health, in a few minutes."

site/src/pages/sending.astro

@@ -3,6 +3,7 @@ import Layout from '../layouts/Layout.astro';
 import HeroAtmosphere from '../components/HeroAtmosphere.astro';
 import Icon from '../components/Icon.astro';
 import CTA from '../components/CTA.astro';
+import PillarPosts from '../components/PillarPosts.astro';
 
 // Single-send trace
 const trace = [
@@ -410,6 +411,15 @@ const faq = [
     </div>
   </section>
 
+  <PillarPosts
+    title="Sending, in more depth"
+    items={[
+      { kicker: 'Limits', href: '/blog/how-many-cold-emails-per-day-per-mailbox/', title: 'How many cold emails can you actually send per day?' },
+      { kicker: 'Planning', href: '/blog/how-many-mailboxes-and-domains-cold-email/', title: 'How many mailboxes and domains do you need?' },
+      { kicker: 'Budgets', href: '/blog/mailbox-budgets-not-server-settings/', title: 'Your send limit is a mailbox budget, not a server setting' },
+    ]}
+  />
+
   <CTA
     title="Connect a mailbox. Send your first campaign today."
     description="OAuth in 30 seconds. Worker assignment is automatic."

site/src/pages/warmup.astro

@@ -628,6 +628,15 @@ for (let wk = 0; wk < 5; wk++) {
     </div>
   </section>
 
+  <PillarPosts
+    title="How warmup actually behaves"
+    items={[
+      { kicker: 'Warmup', href: '/blog/how-email-warmup-actually-works/', title: 'How email warmup actually works, ramp curve and all' },
+      { kicker: 'Policy', href: '/blog/quarantine-early/', title: 'Quarantine early: how we protect shared warmup pools' },
+      { kicker: 'Recovery', href: '/blog/getting-a-mailbox-back-into-warmup-pool/', title: 'Getting a burned mailbox back: a recovery playbook' },
+    ]}
+  />
+
   <CTA
     title="Connect a mailbox. Start warming today."
     description="OAuth in 30 seconds. First warmup send in under a minute."