Mount through TanStack DOM in a Svelte attachment. Remove client prerender and a separate reactive resize pass. Keep responsive definitions, focus options, teardown and the positioned-observation contract. An owned interaction snapshot prevents lazy callback-only derived chains from retaining detached charts; repeated-filter GC stress verifies teardown.

Fixed-settings checkpoint versus QA-fixed layer 3: all charts 4280.4 -> 3163.2 ms, retained dashboard heap 30.1 -> 22.9 MiB; file readiness 654.3 -> 487.1 ms. The mount bundle inventory reused a directory and is invalid; later fresh exports and the final build validate bundle savings. Three browser samples per page.

Checkpoint measurements above predate the final QA lifecycle/coverage fixes and are not isolated shipping effects. Combined shipping benchmark: 477.2/2934.3 ms default visible/all charts, 114 ms observed initial TBT, 18.2 MiB retained heap and 191.1 KiB gzip JS. Original baseline: 509.1/3258.9 ms, 130 ms, 18.3 MiB, 228.1 KiB. Layer 3: 569.3/4271.3 ms, 159 ms, 29.9 MiB, 202.4 KiB. Baseline dates, five API runs, three fresh contexts per page and one warmup; no concurrent QA/build/dev work. Shipping artifacts: /tmp/atlantis-frontend-overhaul/perf/layer4-shipping/results.json. Full gates pass with 220 web and 70 e2e tests.