feat(mlsysim): unify navbar with Subscribe button to match Labs/Kits

Add subscribe-modal.js and Subscribe navbar button to MLSYSIM docs
site, matching the unified navbar pattern across all components
(Labs, Kits, MLSYSIM). Right-side items now follow the same order:
Downloads, Star, Support, Subscribe, GitHub.

Author: profvjreddi

mlsysim/docs/config/_quarto-html.yml

@@ -12,18 +12,18 @@ project:
     - mlsysim-paper.pdf
 
 website:
-  title: "MLSys·im"
+  title: "MLSys·IM - Machine Learning Systems"
   description: "First-principles infrastructure modeling for ML systems — from edge to exascale."
   site-url: https://mlsysbook.ai/mlsysim/
   favicon: logo.svg
 
   open-graph:
     locale: en_US
     site-name: "Machine Learning Systems"
-    title: "MLSys·im — ML Systems Infrastructure Modeling"
+    title: "MLSys·IM — ML Systems Infrastructure Modeling"
     description: "Predict ML system performance, cost, and carbon from first principles. Companion to the ML Systems textbook."
   twitter-card:
-    title: "MLSys·im — ML Systems Infrastructure Modeling"
+    title: "MLSys·IM — ML Systems Infrastructure Modeling"
     description: "Predict ML performance, cost, and carbon from first principles. Open source."
     card-style: summary
 
@@ -35,16 +35,17 @@ website:
   search:
     keyboard-shortcut: ["/"]
 
-  # Navbar — ecosystem dropdown only; page nav lives in the sidebar
+  # Navbar — matches ecosystem pattern; page nav lives in the sidebar
   navbar:
     background: light
+    logo: logo.svg
     search: true
     pinned: true
     collapse: true
     collapse-below: "md"
-    title: "MLSys·im"
+    title: "Machine Learning Systems"
     left:
-      - text: "Ecosystem"
+      - text: "MLSys·IM"
         menu:
           - icon: book-half
             text: "Full Textbook"
@@ -64,13 +65,20 @@ website:
             text: "Hardware Kits"
             href: ../kits/
           - icon: calculator
-            text: "MLSys·im"
+            text: "MLSys·IM"
             href: ./
           - text: "---"
           - icon: lightbulb
-            text: "Labs (Coming 2026)"
+            text: "Labs"
             href: ../labs/
     right:
+      - icon: download
+        text: "Downloads"
+        menu:
+          - icon: file-pdf
+            text: "MLSys·IM Paper PDF"
+            href: mlsysim-paper.pdf
+            target: _blank
       - icon: star
         text: "Star"
         href: https://github.com/harvard-edge/cs249r_book#support-this-work
@@ -79,6 +87,10 @@ website:
         text: "Support"
         href: https://opencollective.com/mlsysbook
         target: _blank
+      - icon: envelope
+        text: "Subscribe"
+        href: "#subscribe"
+        id: "navbar-subscribe-btn"
       - icon: github
         text: "GitHub"
         menu:
@@ -229,6 +241,9 @@ format:
           <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin>
           <link href="https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700&family=JetBrains+Mono:wght@400;500&display=swap" rel="stylesheet">
           <meta name="theme-color" content="#0284C7">
+    include-after-body:
+      - text: |
+          <script src="scripts/subscribe-modal.js" defer></script>
 
 # Announcement bar configuration
 metadata-files: