feat(beliefs): source reliability by domain, never global

A source's track record is kept per (evidence family, belief subject) and
updated only by outcomes: predictions derived from a belief resolving, and
operators marking a belief wrong. With three or more outcomes in a domain
the record adjusts the credibility of that source's new evidence in that
domain, and the adjustment is written on the evidence row. Standing in one
domain never moves standing in another, and the trust-level credibility
constants are never rewritten. Migration 0021 is additive; belief pages
show each cited family's record in the belief's domain.

web/templates/pages/belief_detail.html

@@ -27,7 +27,8 @@
       <div class="card">
         <h2>Evidence for</h2>
         <ul class="plain ev">{{range $d.Evidence}}{{if eq .Direction "for"}}<li class="{{if .Retracted}}retracted{{end}}"><div><strong>{{conf .Weight}}</strong> × cred {{conf .Credibility}} <span class="badge">{{.Kind}}</span> {{if .Retracted}}<span class="badge danger">retracted</span>{{end}}</div><div>{{.Note}}</div><div class="muted small">{{.Source}} · {{ago .CreatedAt}} {{if and (eq .Kind "event") .RefID}}· <a href="/events/{{.RefID}}">event</a>{{else if and (eq .Kind "memory") .RefID}}· <a href="/minds/{{$m.Slug}}/memory/{{.RefID}}">memory</a>{{else if and (eq .Kind "belief") .RefID}}· <a href="/minds/{{$m.Slug}}/beliefs/{{.RefID}}">belief</a>{{end}}</div><div class="muted small">provenance: <span class="badge small">{{.Derivation}}</span> family <code>{{.Family}}</code>{{if eq .ProvenanceStatus "legacy_unknown"}} <span class="badge warn small" title="written before ancestry was recorded; family is the source string">legacy</span>{{end}}{{range .RootIDs}} · <a href="/events/{{.}}">root</a>{{end}}</div></li>{{end}}{{else}}<li class="muted">None.</li>{{end}}</ul>
-        {{if $bd.Families}}<h3 class="small muted">Independent sources</h3><table class="table compact"><thead><tr><th>Family</th><th></th><th class="num">Items</th><th class="num">Primary</th><th class="num">Counts as</th></tr></thead><tbody>{{range $bd.Families}}<tr><td><code>{{.Family}}</code></td><td class="small">{{.Direction}}</td><td class="num">{{.Items}}</td><td class="num">{{.Primary}}</td><td class="num">{{printf "%.2f" .Contribution}}</td></tr>{{end}}</tbody></table><p class="small muted">Within a family the strongest primary item counts in full and further items add a quarter each (capped at 1.5×); derived items count only when the family has no primary item. Diversity counts families: {{$bd.SourcesFor}}.</p>{{end}}
+        {{if $bd.Families}}<h3 class="small muted">Independent sources</h3><table class="table compact"><thead><tr><th>Family</th><th></th><th class="num">Items</th><th class="num">Primary</th><th class="num">Counts as</th></tr></thead><tbody>{{range $bd.Families}}<tr><td><code>{{.Family}}</code></td><td class="small">{{.Direction}}</td><td class="num">{{.Items}}</td><td class="num">{{.Primary}}</td><td class="num">{{printf "%.2f" .Contribution}}</td></tr>{{end}}</tbody></table>{{if $d.Reliability}}<h3 class="small muted">Source reliability in this domain{{with $b.Subject}} ({{.}}){{end}}</h3><table class="table compact"><thead><tr><th>Family</th><th class="num">Right</th><th class="num">Wrong</th><th class="num">Score</th><th></th></tr></thead><tbody>{{range $d.Reliability}}<tr><td><code>{{.Source}}</code></td><td class="num">{{.Correct}}</td><td class="num">{{.Wrong}}</td><td class="num">{{printf "%.2f" .Score}}</td><td class="small muted">{{if .Applied}}applied to credibility{{else}}too little history to apply{{end}}</td></tr>{{end}}</tbody></table>{{end}}
+        <p class="small muted">Within a family the strongest primary item counts in full and further items add a quarter each (capped at 1.5×); derived items count only when the family has no primary item. Diversity counts families: {{$bd.SourcesFor}}.</p>{{end}}
       </div>
       <div class="card">
         {{if $d.Assertions}}<h2>Who said so</h2>