v0.3.0: finish Async Embedding Gateway — mark-vector-stale, cron, defskill, ROADMAP updates

- Add mark-vector-stale(id, content): sets :vector to :pending, queues for re-embed
- Register cron job (embed-all-pending every 10m on :reflex tier via orchestrator)
- Add defskill :passepartout-system-model-embedding (priority 70)
- Remove embedding from topological-sort exclusion list in core-skills
- Export mark-vector-stale in core-defpackage
- Contract: items 4 (mark-vector-stale) and 5 (cron registration)
- Test: test-mark-vector-stale (5 checks)
- ROADMAP: mark Context Manager, Async Embedding Gateway, TUI Experience as DONE
- All v0.3.0 items now complete. Total: 5 suites, 85 checks, 0 failures

org/core-skills.org

@@ -201,7 +201,6 @@ Both ~.org~ and ~.lisp~ files are included. For each skill, the ~.org~ file supp
                                     (string= n "core-manifest")
                                     (string= n "security-dispatcher")
                                     (string= n "system-model-router")
-                                    (string= n "system-model-embedding")
                                     (string= n "system-model-explorer")
                                     (string= n "gateway-tui"))))
                            all-files))