PJ4 top-level docs/

This folder is for cross-cutting documentation only — material that doesn't fit inside any single module's docs/ folder.

Qt toolchain: PJ4 builds against the Qt version pinned in ../versions.env (currently Qt 6.11.1). Install it with the repo-root ../install_qt6.sh. See QT_NOTES.md for what changed since 6.8.

Examples of what belongs here:

• Porting strategy / migration notes that span multiple modules.
• Glossary or terminology references used across the repo.
• Architecture decision records (ADRs) for choices that affect multiple modules.
• Research notes that informed multiple modules' designs — under research/.
• Work-in-progress design specs for modules that don't yet have their own docs/.

What does NOT belong here

• Module-local intent docs (REQUIREMENTS, ARCHITECTURE, USER_MANUAL, …) — those live in <module>/docs/. Examples in this repo: pj_scene2D/docs/, pj_marketplace/docs/.
• Plan documents that are repo-wide — PJ4_PLAN.md lives at the repo root.
• Agent-management state (.remember/, .claude/, .agents/) — those are not human-readable docs.

Current contents

Path	Status	Notes
QT_NOTES.md	Reference	Qt 6.11.1 baseline. Features new since 6.8 (likely past most models' training cutoff), deprecations, and build/platform floors. Read before using an unfamiliar Qt API or reaching for a 6.8-era workaround.
undo_redo_integrity_plan.md	Plan (delivered)	Consolidated undo/redo state-integrity delivery plan: dataset identity, transactional undo, timeline-state snapshots, processor/scene persistence — five incremental PRs (#373 #377 #379 #380 #382, all merged) distilled from two prior solution branches.
was_pending_followup_plan.md	Plan (draft)	Follow-up to the state-integrity epic: unified was-pending semantics for scene restore queues — serialize binding state instead of origin so exact-restore correctness is structural rather than shell-maintained.
research/dataset_format_comparison.md	Reference	Cross-cutting comparison of MCAP, RLDS, LeRobot, Zarr. Informs pj_scene2D and any future dataset-format work.
research/rerun_notes.md	Reference	Analysis of Rerun's 2D architecture; comparison input for pj_scene2D and (potentially) pj_scene3D.

Where to find module docs

See the "Module documentation index" in the top-level CLAUDE.md. Each PJ4 module owns a CLAUDE.md at its root and, when warranted, a docs/ folder with REQUIREMENTS.md / ARCHITECTURE.md.