test: rebuildable bundles, npm test entry point

- esbuild alias fixed in the session/sysinfo/sftp test commands (they
  could not build at all), .sftp-svc.mjs build documented, real
  connection-stability assertions
- tests/build-bundles.cjs builds every bundle fresh; npm test runs the
  seven offline suites; esbuild pinned in devDependencies
- remove the assertion-less .exact-inline.mjs; ignore/clean test temp dirs

.gitignore

@@ -33,6 +33,9 @@ release/
 # stray local test artifacts
 .min-test.bin
 .min2-test.bin
+.exact-test.bin
+tests/.zm-src-*/
+tests/.zm-out-*/
 
 # release notes drafts (consumed by scripts/release.cjs + sync-changelog.cjs)
 RELEASE_NOTES*.md