[plainprogrammer]

Summary

Fixes the Back-button flake that failed PR #8's CI (run 37051089826): after filtering, Back to /collection showed "3 of 5 items" instead of "5 items".

Root cause. Turbo 8.0.23's frame advance (turbo-frame#results + data-turbo-action="advance") does this:

1. Pushes the URL.
2. Swaps the frame.
3. Waits two repaints (FrameRenderer#render).
4. Only then calls session.visit, which sets html[aria-busy] and runs navigator.stop().

Nothing is marked busy during step 3, so wait_for_turbo_idle passes. If Back lands in that gap, the late visit cancels the Back visit and the filtered page stays. The no-cache meta from #7 (fc8cff1) closed a different race (the snapshot cache), not this one.

Fix. The collection and search filter forms and their pagination are now plain Turbo Drive GET visits. Both pages keep turbo-cache-control: no-cache, so Back and Forward refetch them.

Changes

• Removed the results turbo-frames and the frame-only _top targets. The frame: local on the pagination partial is gone.
• Added two regression specs in spec/system/back_navigation_spec.rb. They slow repaints and delay the unfiltered fetch, which reproduces the race deterministically. Both fail on main.
• Removed the url-sync Stimulus controller, which is dead now that these pages are never restored from a snapshot. The Back/Forward field specs pass without it.
• Simplified wait_for_turbo_idle: the frame check and the frames: false workaround are gone.
• Updated the app's pattern docs: SearchResults (records the deviation), Pager, ViewSwitchForm, TileAdd.
• Updated the memory notes on the Turbo quirks and the PR feat: design system, accounts, adding cards and the collection grid (004) #5 follow-ups.

Design-system deviation

The design system's README says "the results sit in a Turbo Frame the form targets". This PR deliberately departs from that (maintainer ruling, 2026-10-02). The exported README.md, components/FilterBar.md and components/CollectionPage.md still describe the frame. They are left as exported, so the change needs to go into the published design system before the next export.

Behaviour notes

• A new search or page now scrolls to the top instead of updating the results in place. Spec 004 AC-6.1 and AC-11.4 still hold: the URL carries the state, Back works, and there is no full page load (window state survives, as the __marker specs check).
• Layout was not compared visually against the previews; the phone-width and narrow-page specs pass.

Test plan

• bin/ci passes locally (484 examples, 0 failures)
• New regression specs fail on main and pass on this branch
• GitHub CI green

🤖 Generated with Claude Code