web: add proof-anatomy section; precision + robustness FAQ

Explain what a proof is (a chain that begins and ends at the user's own
clock, threading through neighbor heartbeats to bracket the event) and
why it can't be cheated in either direction: you can't forge the past
(the fabric has set and the math rejects mismatched links) and you can't
pre-compute the future (the ledger acts as an oracle for reality that
faked-ahead media must agree with). Sharpen the precision FAQ to depend
on the nodes' heartbeat interval, and add a robustness FAQ covering the
built-in neighbor redundancy.

Author: levy

index.html

@@ -356,6 +356,7 @@
     <nav class="nav-links" aria-label="Primary">
       <a href="#problem">The problem</a>
       <a href="#idea">The idea</a>
+      <a href="#proof">The proof</a>
       <a href="#uses">Use cases</a>
       <a href="#compare">Compare</a>
       <a href="#quickstart">Quickstart</a>
@@ -461,6 +462,32 @@ <h2>A clock nobody owns.</h2>
     </div>
   </section>
 
+  <!-- PROOF -->
+  <section id="proof" class="section-alt">
+    <div class="wrap">
+      <div class="section-head reveal">
+        <p class="eyebrow">Anatomy of a proof</p>
+        <h2>A chain that begins and ends at your own clock.</h2>
+      </div>
+      <div class="lede reveal">
+        <p class="drop">A proof is a <b>chain</b>. It sets out from the clock you trust, threads through the steady heartbeats of nodes across the network, reaches the event in question, and comes all the way back — pinning it between one tick that came provably <b>before</b> and one that came provably <b>after</b>.</p>
+        <p>Each heartbeat carries a signed nod to the neighbors it just heard from. Follow those nods outward from your event and, hop after hop, they lead back to a clock you chose to measure against — your own, a lab's, a notary's. The two bracketing ticks are your time bounds; the reference clock at each end is what turns them into a date you can read. Nothing in the chain is asserted after the fact — it's the record of nods that actually happened, in the order they happened, which is exactly why it can't be re-told two ways.</p>
+      </div>
+      <div class="grid g-2 reveal" style="margin-top: 2.6rem;">
+        <div class="card">
+          <div class="ico"><svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="1.6" stroke-linecap="round" stroke-linejoin="round" aria-hidden="true"><path d="M3.5 12a8.5 8.5 0 1 0 2.7-6.2"/><path d="M3 4.5V9h4.5"/><path d="M12 8v4.3l3 1.8"/></svg></div>
+          <h3>You can't forge the past</h3>
+          <p>The moment a heartbeat is woven in, your neighbors have echoed it and stacked their own ticks on top. To move a past event you'd have to rewrite every link that followed — on every machine that already holds a copy. The fabric has set, and the math rejects any chain whose links don't line up.</p>
+        </div>
+        <div class="card">
+          <div class="ico"><svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="1.6" stroke-linecap="round" stroke-linejoin="round" aria-hidden="true"><circle cx="12" cy="12" r="2.4"/><path d="M7 7a7 7 0 0 0 0 10M17 7a7 7 0 0 1 0 10M9.4 9.4a3.6 3.6 0 0 0 0 5.2M14.6 9.4a3.6 3.6 0 0 1 0 5.2"/></svg></div>
+          <h3>You can't pre-compute the future</h3>
+          <p>Say you fake a protest — photos and video generated by AI weeks ahead — then publish them on the day so they look live. To hold up, your event has to agree with everything else the network recorded at that instant: the ledger acts like an oracle for reality. Did the weather station's proven readings match your footage? A camera down the street? Depending on precision, even a traffic light's timing can contradict your video. You can't prepare the present in advance — you'd have to forge it exactly as it unfolds, which is far harder.</p>
+        </div>
+      </div>
+    </div>
+  </section>
+
   <!-- HOW -->
   <section id="how" class="section-alt">
     <div class="wrap">
@@ -700,7 +727,7 @@ <h2>The things people ask first.</h2>
         </details>
         <details>
           <summary>How precise is a proof?<span class="plus"></span></summary>
-          <p>A proof brackets your event within a short window — on the order of under a minute — measured against the clock you choose to prove it against. It's a rigorous bound, not a claim of an exact instant.</p>
+          <p>It depends on the network. How tight the window is comes down to the heartbeat interval of the nodes on the chain — which might be well under a second, or more than a minute. Faster-ticking nodes give a tighter bracket, slower ones a wider one; as a general rule, expect something on the order of a minute or less, measured against the clock you choose to prove it against. Either way it's a rigorous bound, never a claim of an exact instant.</p>
         </details>
         <details>
           <summary>Is my content made public?<span class="plus"></span></summary>
@@ -714,6 +741,10 @@ <h2>The things people ask first.</h2>
           <summary>Who runs the network?<span class="plus"></span></summary>
           <p>Anyone. People, companies, cities, courts, laboratories, even sensors and IoT devices. The more participants there are, the tighter and more widely trusted the proofs become.</p>
         </details>
+        <details>
+          <summary>How robust is the network?<span class="plus"></span></summary>
+          <p>Every node keeps several neighbors, not just one, and each heartbeat is heard and echoed by many of them. That redundancy is built in from the start: links and routes overlap heavily, so nodes dropping offline — or whole regions falling quiet — leave the fabric intact and existing proofs verifiable. The more densely the network is woven, the more resilient it becomes.</p>
+        </details>
         <details>
           <summary>Does it keep working as the network grows and changes?<span class="plus"></span></summary>
           <p>A proof traces the network as it was when your event happened — not as it looks today — so peers coming and going never invalidates an old proof. To stay fast as the network grows, a lookup heads straight for its destination where the route is known and falls back to a bounded search where it isn't. However it's found, every proof is re-checked by the math, so a wrong turn can only make a lookup miss — never make it lie.</p>