P3-X: Ensure P3 polish & ship work meets DESIGN

[devlux76]

Note: DESIGN has been moved into the wiki, located https://github.com/devlux76/cortex/wiki

This is a super-task for finishing the remaining P3 work (polish & ship). It should be a child of the existing P3 tracker (#72). Close each subtask issue as it is verified complete; this issue remains open until all checklist items are done.\n\n### Subtasks (close the relevant issue when done)\n- [ ] Ensure WebGL embedding provider is fully functional and tested. (Related: #36)\n- [ ] Ensure Experience Replay is fully implemented and has coverage. (Related: #37)\n- [ ] Ensure Cluster Stability is complete and tested, including volume deletion behavior. (Related: #38)\n- [ ] Ensure Benchmark suite experiments run reliably and results are documented. (Related: #39)\n- [ ] Ensure CI hardening is in place and workflows are stable. (Related: #40)\n- [ ] Ensure Documentation is synced with implementation and accurate. (Related: #41)\n- [ ] Ensure Product-surface UX contract docs are up to date and correct. (Related: #42)\n\n### Completion guidelines\n- Close each source issue (e.g., #36, #37, #38, #39, #40, #41, #42) as soon as the implementation satisfies the acceptance criteria.\n- Keep this issue open until all checklist items are complete and the system matches the P3 design expectations.\n\n> NOTE: This is a tracking issue; it does not implement behavior itself. It exists to coordinate completion across the individual subtasks and ensure none are left behind.,labels:[P3: low]