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/openapi_routeprefix_smoke_reverseproxy.csv

@@ -92,7 +92,7 @@
 "ReverseProxy","/vexhub","https://vexhub.stella-ops.local",,
 "ReverseProxy","/vexlens","http://vexlens.stella-ops.local",,
 "ReverseProxy","/orchestrator","http://orchestrator.stella-ops.local",,
-"ReverseProxy","/taskrunner","http://taskrunner.stella-ops.local",,
+
 "ReverseProxy","/cartographer","http://cartographer.stella-ops.local",,
 "ReverseProxy","/reachgraph","http://reachgraph.stella-ops.local",,
 "ReverseProxy","/doctor","http://doctor.stella-ops.local",,