docs: classify loader smoke support surface

packages/support/loader-smoke/README.md

@@ -5,3 +5,13 @@ Shared subprocess harness for keyless example smokes that boot the real stdio-ag
 Successful runs return stdout and stderr only after a zero exit. Non-zero exits and deadlines reject with both captured streams. `LOADER_SMOKE_TEST_TIMEOUT_MS` leaves Vitest enough room for the process-owned diagnostic timeout to fire first.
 
 This is support-tier test infrastructure, not product API. The consumers are the Loader-path smokes under `examples/{echo-agent,coding-agent,cordis-agent}`.
+
+## Model Experience
+
+None, as this test-only harness boots example processes and inspects their streams without changing an assembled model request.
+
+## Known Limitations and Deferred Work
+
+- **Only the unbuilt tsx/Loader path is exercised** — built-bin artifacts remain the responsibility of their separate e2e smokes.
+- **Captured stdout and stderr are unbounded** — a runaway child can consume memory until the deadline kills it.
+- **Timeout kills only the direct child** — a process tree spawned by a faulty fixture can outlive the smoke and needs external cleanup.