Add bounded capacity command execution

[akua-agentos]

Summary

• add hand-written execution overlays for the reviewed cluster, compute-config, instance-type, and machine-list reads
• preserve fixed production routing, canonical-ID validation, public-token precedence, structured errors, and fail-closed machine-create confirmation
• document executable overlays separately from the discovery-only generated registry and pin selected OpenAPI contracts

Validation

• bun test test/capacity-commands.test.ts test/capacity-openapi.test.ts test/cli.test.ts test/docs.test.ts (34 passed)
• git diff --check
• generated drift check completed successfully during the initial check attempt

Local tool boundary

mise run check unexpectedly started automatic tool installation and was interrupted; it was not retried. Its build leg could not find tsc, and six release tests could not find zip. This boundary did not change repository files. No live Akua API, machine mutation, merge, or release was performed.