[Coasterpete]

M168: Interactive Authoring Reliability and Timing

Summary

This PR implements the M168 interactive authoring reliability and timing work on top of the merged M167 interactive authoring foundation.

The focus is on backend stability, deterministic preview lifecycle management, and workspace-owned projection timing instrumentation while preserving renderer neutrality and avoiding UI-specific dependencies.

Included

• Complete M168.1 reliability baseline
• Preserve structured preview diagnostics
• Add coherent preview lifecycle snapshots
• Add Deliverable 4A backend timing measurements
• Add Deliverable 4B correlated editor projection timing
• Add deterministic regression tests covering timing correlation and lifecycle behavior

Design

• Keeps instrumentation owned by EditorWorkspace
• Introduces a monotonic timing tracker for authoring projections
• Correlates:
  • Request submission
  • Workspace acceptance
  • Projection completion
  • First workspace publication
  • Retirement
  • Engineering snapshot capture
  • Viewport snapshot capture
• Uses immutable timing records
• Treats instrumentation as observational only and never changes editor behavior
• Maintains renderer neutrality with no Avalonia-specific timing dependencies

Testing

Validated with:

• Focused M168 timing tests
• Editor regression tests
• Track authoring test suite
• Full solution test suite

All tests passed successfully.

Notes

This branch was recreated from the current main branch to avoid replaying historical M167 commits that had already been merged. As a result, this pull request contains only the new M168 implementation work, producing a clean and reviewable commit history.