feat(site): 🫙 PCBJam landing revisions — branding, accuracy, positioning graphic

Founder review pass on the landing page, plus commit the landing-page
research/spec docs under features/lp.

Branding & assets:
- New PCBJam mark: convert the jam-jar image to favicon.svg (trimmed, rounded
  tile) and use it in the browser tab, header, and footer.
- Footer "Built by": flower mark + "Emergence Engineering" in white Oswald (the
  blog's title font, self-hosted via @fontsource) so it's legible on dark.
- Produce the positioning quadrant graphic (public/graphics) and drop the placeholder.

Copy / accuracy:
- Remove header GitHub link; point "Built by EE" + footer "About" to
  emergence-engineering.com; Built-by CTA -> mailto:contact@emergence-engineering.com.
- Replace the wrong testimonial with Greg Detre's real quote from EE's site.
- Drop blog icons from Multiplayer/Pillars/How-it-works; add "Coming soon" to
  live-cursors & pin-comment; drop the hard-coded Yjs mention.
- Rework monetization to free+local / paid cloud-sync; remove "no metered AI",
  "no per-seat toll", and the Flux price claim; soften the AI section.
- Reframe waitlist copy (incl. confirmation email) to newsletter + early access.

Fixes:
- Offset only #waitlist for the sticky header (scroll-margin-top); section
  anchors keep their original behavior.

Docs:
- Commit features/lp (copy spec, brand guide, competitive research) via force-add
  over the /features/ gitignore.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

site/public/graphics/positioning-quadrant.svg

@@ -0,0 +1,60 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 820 600" width="820" height="600" role="img" aria-labelledby="pq-title pq-desc" font-family="system-ui, -apple-system, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif">
+  <title id="pq-title">PCB tool positioning map</title>
+  <desc id="pq-desc">A quadrant chart. The horizontal axis runs from desktop-install on the left to browser-native on the right; the vertical axis from proprietary at the bottom to open at the top. LibrePCB and KiCad sit top-left (open but desktop). KiCanvas sits top-right but is viewer-only. Flux and EasyEDA sit bottom-right (browser but proprietary). Altium 365 and OrCAD X sit bottom-left (desktop and proprietary). PCBJam sits alone in the top-right as the only browser-native, open, real-time-multiplayer tool.</desc>
+
+  <!-- panel -->
+  <rect x="8" y="8" width="804" height="584" rx="16" fill="#11182e" stroke="#233052" stroke-width="1"/>
+
+  <!-- top-right "whitespace" tint -->
+  <rect x="410" y="64" width="338" height="232" fill="#4f7cff" fill-opacity="0.09"/>
+
+  <!-- axes -->
+  <g stroke="#34436b" stroke-width="2" fill="#34436b">
+    <line x1="80" y1="296" x2="748" y2="296"/>
+    <line x1="410" y1="64" x2="410" y2="528"/>
+    <polygon points="748,296 734,289 734,303" stroke="none"/>
+    <polygon points="80,296 94,289 94,303" stroke="none"/>
+    <polygon points="410,64 403,78 417,78" stroke="none"/>
+    <polygon points="410,528 403,514 417,514" stroke="none"/>
+  </g>
+
+  <!-- axis labels -->
+  <g fill="#9aa6c0" font-size="14" font-weight="600">
+    <text x="410" y="50" text-anchor="middle">Open &amp; yours</text>
+    <text x="410" y="554" text-anchor="middle">Proprietary, locked-in</text>
+    <text x="92" y="316" text-anchor="start">Desktop install</text>
+    <text x="736" y="316" text-anchor="end">Browser-native</text>
+  </g>
+
+  <!-- competitors -->
+  <g fill="#8794ad">
+    <circle cx="210" cy="150" r="5"/>
+    <circle cx="250" cy="205" r="5"/>
+    <circle cx="540" cy="200" r="5"/>
+    <circle cx="540" cy="372" r="5"/>
+    <circle cx="596" cy="440" r="5"/>
+    <circle cx="210" cy="388" r="5"/>
+    <circle cx="250" cy="448" r="5"/>
+  </g>
+  <g fill="#b4bfd6" font-size="15">
+    <text x="224" y="155">LibrePCB</text>
+    <text x="264" y="210">KiCad</text>
+    <text x="554" y="205">KiCanvas</text>
+    <text x="554" y="377">Flux</text>
+    <text x="610" y="445">EasyEDA</text>
+    <text x="224" y="393">Altium 365</text>
+    <text x="264" y="453">OrCAD X</text>
+  </g>
+  <text x="554" y="222" font-size="11" fill="#6b7796">viewer only</text>
+
+  <!-- PCBJam marker (the only "all three") -->
+  <circle cx="590" cy="120" r="30" fill="#4f7cff" fill-opacity="0.12"/>
+  <text x="590" y="130" text-anchor="middle" font-size="30" fill="#32d583">★</text>
+  <text x="614" y="128" text-anchor="start" font-size="19" font-weight="700" fill="#e7ecf5">PCBJam</text>
+  <rect x="560" y="140" width="170" height="24" rx="12" fill="#32d583" fill-opacity="0.15" stroke="#32d583" stroke-opacity="0.6"/>
+  <text x="645" y="156" text-anchor="middle" font-size="12" fill="#32d583" font-family="ui-monospace, SFMono-Regular, Menlo, Consolas, monospace">real-time multiplayer</text>
+
+  <!-- legend -->
+  <text x="34" y="580" font-size="14" fill="#32d583">★</text>
+  <text x="50" y="580" font-size="12" fill="#9aa6c0">= true real-time multiplayer (PCBJam only)</text>
+</svg>