[docs] Separate current guidance from obsolete plans and historical evidence #339

Why

Clean up the docs before we write subsystem designs or settle the overall architecture. The existing docs index already calls for one home per fact and separates plans from implementation. Some older pages still mix superseded proposals, implementation notes, and one-off validation, making it easy for developers and agents to pick up stale guidance.

What we’re borrowing from Magpie

• Now: Follow Magpie’s subsystem docs conventions: give each current contract one home, link to the source rather than copying implementation, and keep superseded plans and historical evidence separate from current guidance. This issue is the cleanup step.
• Later, after OpenDirector agrees on its architecture boundaries: Write source-linked subsystem references that explain responsibilities, state transitions, failure and recovery behavior, and how to verify them. Follow Magpie’s AGENTS.md by routing agents to the relevant reference before they change code; update the owning reference in the same PR when a contract changes.
• Close the feedback loop: Use Magpie’s LESSONS.md as a model for recording real failures, what would have caught them, and the supporting evidence. Promote recurring lessons into regression tests or review rules. These follow-on design and workflow changes are not part of this cleanup.

Suggested first pass

• Keep the active docs index focused on maintained guides and development references. Give dated provider/platform validation and completed handoffs a clearly marked historical section.
• Reduce four old canvas plans to short notes at their existing URLs that point to the implemented source and the commit-pinned original. Check the implementation where a note describes current behavior; do not carry old measurements forward as current evidence.
  • Reference catalog preloading: the opening still calls the design unconfirmed, while later sections record implementation; two sections describe different default views.
  • Generation node defaults: the proposed write-on-open was superseded by read-only resolution.
  • Video hover playback: early playback design differs from the implementation notes, and the page contains outdated recovery advice.
  • Node information button: retain the original feature plan and counting rationale as historical context; point to the current component rather than restating planned wiring.
• Move the #87 Windows handoff out of the active reading order without deleting the bilingual handoff or its unique validation evidence. Treat the merged #193 implementation and the status of the parent issue separately.

Acceptance

• Old file URLs remain useful, relative links resolve, and original decisions, evidence, and limitations remain reachable at immutable revisions.
• Keep bilingual user guides and unique validation records. Do not delete an unlinked file just because it has no inbound links.
• Keep this docs-only: no runtime, CI, or release-policy changes. Do not treat the existing architecture drafts as final or use this issue to decide new subsystem boundaries.