refactor(jobengine): delete TaskRunner service

- Remove TaskRunner source, tests, libraries (3 directories)
- Remove from compose, services-matrix, nginx, hosts, smoke tests
- Remove CLI commands, UI references, Authority scopes
- Remove docs, OpenAPI spec, QA state files
- Leave task_runner_id DB columns as nullable legacy
- PacksRegistry preserved (independent service)
- Eliminates 2 containers (taskrunner-web + taskrunner-worker)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

devops/compose/envsettings-override.json

@@ -21,7 +21,7 @@
                         "airgapController":  "https://stella-ops.local",
                         "gateway":  "https://stella-ops.local",
                         "doctor":  "https://stella-ops.local",
-                        "taskrunner":  "https://stella-ops.local",
+
                         "timelineindexer":  "https://stella-ops.local",
                         "timeline":  "https://stella-ops.local",
                         "packsregistry":  "https://stella-ops.local",