refactor(ci): split orchestrator tests into per-PR health checks and nightly exhaustive suite

validate-orchestrator.yml (per-PR, ~5 min):
  - Plugin architecture health: compilation, unit tests, plugin loader
    graceful degradation, installed service validation, type declaration checks

validate-orchestrator-integration.yml (daily 3 AM UTC cron, ~1-2h):
  - 5 parallel jobs mirroring orchestrator-integrity.yml:
    plugin-interface, k8s (5 tests), aws (10 tests),
    local-docker (9 tests), rclone (1 test)
  - Full LocalStack + k3d integration coverage
  - continue-on-error on known flaky end2end tests

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: frostebite