feat(workspace): migrate ArcheAxis desktop A1

[DTALEX66]

Summary

Migrates the verified ArcheAxis desktop A1 slice from legacy PR #15 onto current main without importing its obsolete CI, dependency, configuration, runtime-policy, or release-manifest changes.

Included scope

• ArcheAxis Workspace shell, responsive rail/subnavigation, Jobs/Activity Dock, and truthful route-state UI.
• Inspector accessibility state synchronization across the 960px breakpoint.
• Mobile Inspector closed-state visual fix: the inert panel is fully off-canvas; the external reopen trigger remains operable.
• Browser smoke coverage for responsive ARIA/inert/reopen and off-canvas geometry contracts.
• Product-positioning documentation and Rust formatting-only cleanup.

Explicitly excluded

• Legacy PR feat(workspace): align ArcheAxis learning and knowledge desktop shell #15 CI/workflow, requirements, dependency, configuration, release-manifest, and status-policy changes.
• GitHub Release/tag/assets. app/release-manifest.json remains unreleased / public=false.

Verification

Candidate commit: 29d557b8f925ee14268d4b84bb1b2c959d8de64c

• Three independent read-only reviews of frozen pre-commit tree d144559cdd81e1ca58223281ea8bdcbd27821716: GO; no Critical/High findings.
• scripts/a0_browser_smoke.py — passed against isolated COGNITIVE_DATA_DIR.
• node --check app/workspace/ui/assets/app.js — passed.
• python -m py_compile scripts/a0_browser_smoke.py — passed.
• ruff check scripts/a0_browser_smoke.py — passed.
• uv build --wheel plus packaged CSS marker verification — passed.
• The pre-remediation candidate also completed root deterministic, Knowledge Base, integration, architecture, convention, Rust/Tauri, and wheel gates; exact-SHA CI remains the merge gate for this commit.

Risk and rollback

Risk is limited to the eight paths in this PR, primarily Workspace responsive layout and browser-smoke behavior. No runtime/configuration behavior or public release state is changed.

Rollback after merge: git revert 29d557b8f925ee14268d4b84bb1b2c959d8de64c.