fix(build): include subagent-registry.runtime.js in dist output (#66205)

* fix: ensure subagent-registry.runtime.js is included in dist output

* fix(build): ship subagent registry runtime

* Update CHANGELOG.md

---------

Co-authored-by: Vincent Koc <vincentkoc@ieee.org>

src/infra/tsdown-config.test.ts

@@ -69,6 +69,7 @@ describe("tsdown config", () => {
         "agents/auth-profiles.runtime",
         "agents/model-catalog.runtime",
         "agents/models-config.runtime",
+        "agents/subagent-registry.runtime",
         "agents/pi-model-discovery-runtime",
         "index",
         "commands/status.summary.runtime",