feat(nostr): outbox-model fetching, private mutes, contacts, NIP-56 vocabulary

Closes the four spec gaps from the audit, verified against the NIPs repo.

NIP-65 (kind 10002) — the one that was actually breaking things. Mute lists are
published by each contact to their own write relays, so querying a fixed relay
set finds only the subset who happen to write where this deployment reads. The
trust graph was silently under-fed and counts came out low, which looks like
"nobody muted them" rather than like a bug. Adds a relay-list codec, per-author
grouping with a fallback for accounts that have published no list, and
on-demand relay connections in the transport so an outbox query can reach
relays that were never configured.

NIP-51 private entries — the viewer's own private mutes are now decrypted
through their signer (NIP-44) and applied as viewer mutes. Someone who mutes
privately previously got no effect at all. The privacy boundary is asymmetric
and enforced at the codec: another account's private list is never decoded,
and the check lives there rather than in the caller's discipline.

NIP-02 (kind 3) — the runtime can build the trust graph itself, so
<bitgate-provider> no longer needs a host to supply a follow list. Set
trust="manual" to opt out.

NIP-56 vocabulary — SOCIAL_POLICY declared thresholds for "harassment", which
is not a NIP-56 type, so no standard client could ever trigger it. Replaced
with the defined vocabulary and asserted in tests. Commerce keeps its
marketplace-specific categories, now documented as deliberate, with defaults so
unclassified reports are never silently dropped.

Two bugs found by the new tests:
- checkout had no default threshold, so a flood of "other" reports did nothing
  at the one place money changes hands. Now earns review, never auto-denial.
- describe() spread diagnostics after a derived field, so a stale zero shadowed
  the live relay-list count.

Adds docs/nips.md recording coverage, deliberate choices, and remaining gaps —
NIP-32 labelling being the largest.

811 tests.

packages/widget/src/provider.js

@@ -35,7 +35,7 @@ export function requestContext(element) {
 
 export class BitGateProvider extends globalThis.HTMLElement {
   static get observedAttributes() {
-    return ["relays", "root", "policy", "profile", "application", "namespace", "viewer"];
+    return ["relays", "root", "policy", "profile", "application", "namespace", "viewer", "trust"];
   }
 
   constructor() {
@@ -157,6 +157,15 @@ export class BitGateProvider extends globalThis.HTMLElement {
       );
 
       await this.runtime.loadAdministrativeState();
+
+      // With a viewer known, build the trust graph without the host having to:
+      // fetch their follow list, then read each contact's mute list from that
+      // contact's own write relays.
+      if (this.runtime.viewerPubkey && this.getAttribute("trust") !== "manual") {
+        await this.runtime.loadContacts();
+        await this.runtime.loadTrustedMuteLists();
+      }
+
       this.dispatchEvent(new CustomEvent("bitgate:loaded", { bubbles: true, composed: true }));
     } catch (error) {
       this.error = /** @type {Error} */ (error);
@@ -205,6 +214,12 @@ export class BitGateProvider extends globalThis.HTMLElement {
     this.runtime.signer = signer;
     const pubkey = await signer.getPublicKey();
     this.runtime.setViewer(pubkey);
+
+    if (this.getAttribute("trust") !== "manual") {
+      await this.runtime.loadContacts();
+      await this.runtime.loadTrustedMuteLists();
+    }
+
     return pubkey;
   }
 }