feat: add beliefs with evidence-derived confidence, contradictions and corrections

Phase 6. Beliefs are propositions with a prior set by epistemic kind and a
confidence computed from typed evidence: sigmoid(logit(prior) + slope ×
(support × diversity − opposition)), where support from a single source
is discounted so repetition cannot manufacture certainty, and bounds keep
the mind away from absolute certainty. Every evaluation stores its
breakdown and appends a version row protected by the append-only
trigger; the belief page shows the arithmetic, evidence for and against,
alternatives, contradictions and history.

Contradiction detection is deterministic first (negation plus token
overlap): a hit emits contradiction_detected, links both beliefs and
makes each counter-evidence for the other so both trend to contested.
Operators can assert beliefs (their statement is the evidence), add
evidence, mark a belief wrong (pinned rejected, history kept) and forbid
an inference; do-not-infer corrections block matching hypotheses.
Retracting a memory retracts the evidence that cited it and re-evaluates
the beliefs concerned.

The associate process proposes low-confidence causal hypotheses from
co-occurring notable observations, and the hypothesis handler turns
admitted ones into beliefs with automatic alternatives, closing demo
scenarios 1 and 2 without any model call.

web/templates/pages/mind.html

@@ -42,6 +42,13 @@
     </dl>
   </div>
 </section>
+<section class="grid cols-2">
+  <div class="card">
+    <h2>Important beliefs <span class="muted small"><a href="/minds/{{$m.Slug}}/beliefs">{{.Data.BeliefStats.Total}} total</a></span></h2>
+    {{if .Data.Beliefs}}<table class="table compact"><tbody>{{range .Data.Beliefs}}<tr><td><span class="badge st-{{.Status}}">{{.Status}}</span></td><td><a href="/minds/{{$m.Slug}}/beliefs/{{.ID}}">{{.Proposition}}</a></td><td class="num"><span class="conf"><span class="conf-bar"><i style="width:{{pct .Confidence}}"></i></span> {{conf .Confidence}}</span></td></tr>{{end}}</tbody></table>
+    {{else}}<p class="muted small">No beliefs yet.</p>{{end}}
+  </div>
+</section>
 <section class="grid cols-2">
   <div class="card">
     <h2>Personality brief <span class="muted small">what cognitive prompts receive</span></h2>