feat(workspace): align ArcheAxis learning and knowledge desktop shell

[DTALEX66]

Scope

• align public ArcheAxis OS positioning with the approved local-first, evidence-driven learning and knowledge system
• set Apple-light as the no-preference default while retaining Violet Core and existing theme choices
• preserve real Workspace API boundaries; planned modules remain explicitly unavailable
• fix browser-smoke page-isolation assertion and strengthen real Activity Dock readback coverage

Verification

• uv lock --locked
• python -m pytest tests/test_workspace_api.py tests/test_workspace_job_center.py tests/test_ci_a0_gates.py -q
• python scripts/check_architecture.py
• node --check app/workspace/ui/assets/app.js
• isolated python scripts/a0_browser_smoke.py
• git diff --check

Boundaries

No schema or migration changes, no release-status change, no fabricated API/module status, and no runtime data or credentials.