chore(deps-dev): bump tsdown from 0.11.13 to 0.20.3 in /packages/sdk

Bumps [tsdown](https://github.com/rolldown/tsdown) from 0.11.13 to 0.20.3.
- [Release notes](https://github.com/rolldown/tsdown/releases)
- [Commits](rolldown/tsdown@v0.11.13...v0.20.3)

---
updated-dependencies:
- dependency-name: tsdown
  dependency-version: 0.20.3
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

packages/sdk/package.json

@@ -55,7 +55,7 @@
   "devDependencies": {
     "@types/node": "^22.15.17",
     "async-channel": "^0.2.0",
-    "tsdown": "^0.11.9",
+    "tsdown": "^0.20.3",
     "typescript": "^5.8.3",
     "vitest": "^3.1.3"
   },