release: bump version to 0.74.3

docs/HARNESS.md

@@ -220,9 +220,26 @@ Optional for delivery smoke:
 - Docker daemon for image builds
 - Helm for chart lint/template checks
 
-If a required local tool is missing, do not install system software
-automatically. Report the gap and point to `./planet.sh init` or
-`scripts/bootstrap-dev.sh` as the existing bootstrap path.
+For routine harness validation, do not install missing system software
+automatically. Report the gap and point to the explicit bootstrap entry points.
+`./planet.sh init` can install missing Docker Engine, Compose v2, and Buildx on
+Ubuntu / Ubuntu WSL, start the local service, and configure Docker group access.
+This bootstrap behavior is intentional; do not invoke it merely to make harness
+checks pass. `scripts/bootstrap-dev.sh` only prepares application dependencies.
+
+Docker bootstrap regression checks use isolated command stubs and never install
+packages or modify the host daemon:
+
+```bash
+uv run --frozen --project . python scripts/harness/test_docker_bootstrap.py
+uv run --frozen --project . python scripts/harness/test_database_startup.py
+```
+
+Database startup regressions also run in quick-check. They cover Compose
+reconciliation of existing containers, visible startup errors, published-port
+checks, bounded recreation that preserves volumes, and the backend connection
+gate before schema initialization. Their command stubs and driver mocks do not
+modify the host Docker environment.
 
 ## What Agents Must Not Change Automatically