Add exportState and moduleSnapshot helpers across all module categories.

Fifth pass: complete measurement modules (sla-budget, histogram-gossip) with moduleSnapshot/toJSON; stats-exporter exportSnapshot; exportState() alias on modules with standard snapshot serialization.

Co-authored-by: Cursor <[email protected]>

pear-platform/hyper-bare-headless-ui/index.js

@@ -116,6 +116,10 @@ class HyperBareHeadlessUi extends EventEmitter {
     return this.snapshot()
   }
 
+  exportState () {
+    return this.toJSON()
+  }
+
   sendToUiBatch (messages) {
     if (!Array.isArray(messages)) throw new Error('messages array required')
     return messages.map((m) => this.sendToUi(m.channel, m.payload))