feat: rename to BitGate and close the drop-in gap

Renames the project and makes it as easy to adopt as BitLogin, which was the
stated bar and which it did not previously meet.

Rename (ADR 0005): @nostr-governance/* -> @bitgate/*, governance-* elements ->
bitgate-*, createGovernanceRuntime -> createBitGate. "Governance" reads as DAO
voting to this audience and named a category rather than a product; BitGate
names the benefit and joins the bit- family that BitVid and BitRoad compose
with. Domain types keep their names — the product is BitGate, the subject
matter is still governance. The migration plan is left as written; this ADR
records the change rather than rewriting history.

Drop-in distribution (ADR 0006): adopting BitGate meant supplying a transport,
authoring a policy, and wiring every element in JavaScript. Now:

- createRelayTransport(urls) — WebSocket transport with reconnection, backoff,
  subscription replay, and cross-relay dedupe
- policy presets (social, commerce, admin-only) addressable by name; the engine
  still carries no thresholds of its own
- <bitgate-provider> — configuration in markup, with descendants finding the
  runtime through a bubbling context event rather than DOM walking, which
  breaks across shadow boundaries
- npm run build:widget — a self-contained dist/bitgate.js

That last one came from running it in a browser rather than from a test. Bare
specifiers resolve in Node and vitest but not in a browser, so the widget
source worked everywhere except a plain static page — the one place it exists
to serve. The bundle is not committed: consumers build from reviewed source.

Also found by running it: the provider's ready event fires during element
upgrade, before a page that defines elements after parsing can attach a
listener, so it now exposes `ready` as a promise too.

Four bugs fixed along the way, three found by new tests and one by the browser:
admin state stayed silent when a roster change altered capabilities but no
denials; the relay transport sent every subscription twice on connect; the
commerce preset computed a meaningless visibility verdict at checkout and could
hide a listing from its own seller; <bitgate-status> threw on an unusable
decision.

759 tests; lint, typecheck, and both builds clean.

package.json

@@ -1,5 +1,5 @@
 {
-  "name": "nostr-governance",
+  "name": "bitgate",
   "version": "0.1.0",
   "private": true,
   "type": "module",
@@ -12,7 +12,9 @@
     "build:types": "tsc -p packages/core/tsconfig.types.json && tsc -p packages/nostr/tsconfig.types.json && tsc -p packages/runtime/tsconfig.types.json && tsc -p packages/bitvid-compat/tsconfig.types.json && tsc -p packages/widget/tsconfig.types.json && tsc -p packages/testing/tsconfig.types.json",
     "lint": "npm run check:references && npm run check:types",
     "check:references": "node scripts/verify-no-reference-imports.mjs",
-    "check:types": "tsc -p tsconfig.json --noEmit && tsc -p packages/widget/tsconfig.json --noEmit"
+    "check:types": "tsc -p tsconfig.json --noEmit && tsc -p packages/widget/tsconfig.json --noEmit",
+    "build:widget": "node packages/widget/build.mjs",
+    "build": "npm run build:types && npm run build:widget"
   },
   "engines": {
     "node": ">=22"
@@ -25,6 +27,7 @@
     "@types/node": "^22.10.0",
     "happy-dom": "^20.11.2",
     "typescript": "^5.4.5",
-    "vitest": "^3.2.7"
+    "vitest": "^3.2.7",
+    "esbuild": "^0.28.2"
   }
 }