v0.1.1: remove dependency-only action no-op recipes

[leynos]

Goal

Cut a narrow Netsuke v0.1.1 follow-up after v0.1.0 final, removing the most visible declarative-manifest paper cut discovered during downstream migration without widening into the v0.2.0 execution redesign.

Release gate

• Allow command to be optional if deps are present #572 — allow an action or target with non-empty deps to omit command and lower it as a genuine dependency-only Ninja node.

Scope boundary

v0.1.1 remains a compatibility-preserving manifest polish release. It must not absorb:

• structured command blocks or the action runner;
• manifest inclusion or bundle composition;
• Git-aware planning;
• broad standard-library expansion; or
• unrelated OrthoConfig integration.

Those features remain tracked by #593 and their dedicated RFCs.

Release admission

Before tagging v0.1.1:

• Allow command to be optional if deps are present #572 is merged with manifest, graph-generation, CLI, serial-ordering, deduplication, and failure-propagation regressions;
• Catnap's aggregate all action no longer needs command: ":";
• at least one downstream migration canary exercises a dependency-only aggregate action;
• v0.1.0 manifests remain compatible;
• migration and user documentation show dependency-only aggregate actions as the preferred form;
• package/install paths and the complete repository quality gates pass on the exact release commit.

Related work

• v0.1.0 final: close the three release-blocking manifest/runtime defects #594 gates v0.1.0 final and does not include Allow command to be optional if deps are present #572.
• v0.2.0: land structured recipes, Git-aware change detection, and OrthoConfig v0.10 integration #593 gates v0.2.0 feature work.