The new @stacksjs/bun-router/runtime entry in #896 has deterministic graph and behavior coverage, but fresh-process timing and RSS are currently measured by an ignored one-off script. That makes later entry changes hard to compare and leaves the result tied to one developer machine.
Add a checked-in diagnostic that compares the root and runtime entries after the normal production build. Each variant must run in a fresh process, import and verify the same required serving symbols, force GC before the final RSS reading, and run in alternating order for at least 15 pairs. Preserve every raw sample and report medians, paired median ratios, and the number of pairs where runtime is lower.
Add a manual GitHub Actions workflow using the latest stable Bun. It must upload the JSON result as an artifact and clearly label hosted-runner numbers as diagnostic, not publishable rankings. Record the exact Bun version, executable, OS, architecture, commit, and dirty state.
This supports #896 and downstream stacksjs/stacks#2590. It does not replace the local sampled host-load guard or authorize a stable package release.