refactor: remove molecule_ci_guard — adds complexity, no value

The cross-runner cancellation guard was killing healthy molecule slots
when unhealthy slots failed, defeating fail-fast: false. With fail-fast:
false and no guard, slots on healthy runners complete independently.

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

docs/index.md

@@ -104,8 +104,8 @@ devx is a self-contained Python package under `src/devx/`:
 - **Dev tools** (`devx.tools`) — setup, install_tools, check_test_speed,
   configure_repo, generate_badges, generate_cliff_config, install_checkmake
 - **Molecule tools** (`devx.molecule`) — Optional, for projects with Ansible
-  roles: distribute_molecule, molecule_ci_guard, molecule_all, discover_runners,
-  start_docker, platforms
+  roles: distribute_molecule, molecule_all, discover_runners, start_docker,
+  platforms
 
 See [Architecture](Architecture) for the full package structure, module
 descriptions, design principles, and data flow diagrams.
@@ -132,7 +132,7 @@ devx provides a `devx` CLI with three command groups:
 
 - `devx ci <command>` — CI/CD automation (17 commands)
 - `devx tools <command>` — Developer tools (9 commands)
-- `devx molecule <command>` — Molecule testing (4 commands, optional)
+- `devx molecule <command>` — Molecule testing (3 commands, optional)
 
 See [CLI Commands](CLI-Commands) for full command documentation with examples.