Preserve command cancellation and clean up failed runtime startup

[wolfy-j]

Summary

• preserve the Cobra command context through runtime bootstrap so cancellation, deadlines, and caller values reach loaded components
• keep the latest successful load context when a later component fails
• give each command runtime one cleanup owner shared across pack bootstrap, start, launch, cancellation, and normal shutdown paths
• clean already-loaded components after load/start failures and make affected dispatchers tolerate cleanup before Start

The change reuses the existing loader and shutdown pipeline. It adds one parent-aware bootstrap entry point and one command-local one-shot cleanup owner; no runtime protocol or configuration surface is introduced.

Regression coverage

Tests cover parent cancellation/value/deadline propagation, partial-load cleanup, pre-start dispatcher cleanup, pack-start failure, normal shutdown, cancellation without a signal, and prevention of duplicate shutdown.

Verification

• uncached race tests for boot, command runtime, store/WebSocket dispatchers, event bus, and security dispatcher
• go vet
• golangci-lint v2.13.2: 0 issues
• Windows amd64 build of affected packages
• go mod verify
• git diff --check