[Resource Consumption] minimized iframes consume resources and are unbounded

[nedtwigg]

Minimized iframe surfaces retain their live documents without a count limit so minimizing another browser never discards unsaved page state or turns reattachment into a reload.

Hidden iframes can still consume memory and run JavaScript, timers, sockets, and media. Retaining arbitrarily many minimized iframes therefore allows resource consumption to grow without a Dormouse-imposed bound.

Priority: low. This is an accepted tradeoff for preserving content state. A future improvement could warn users when retained iframe resource use is high. Do not silently evict or reload minimized documents to enforce a cap.

The current eight-surface parking cap is being removed as part of the minimize/reattach lifecycle fix. This issue tracks the resource-consumption follow-up, not reintroducing that cap.

[dormouse-bot]

Tracking issue, no code change — but the premise isn't in the tree yet, which changes what the follow-up is tracking.

On main (10837e7a) the eight-surface cap is still live, and no open PR or remote branch removes it. So today's behavior is the one this issue rules out rather than the unbounded retention it describes: parkedWith silently drops the oldest park, and the evicted Door reattaches by reloading with the latest URL/session params. Retention becomes unbounded only when the lifecycle fix lands.

Three places state eviction as the contract and have to move in that same change, or the removal ships alongside a spec and two tests asserting the opposite: the Bounded. bullet in tiling-engine.md → "Parked leaves", doorLeaf caps the parked DOM itself, evicting oldest-first, and the cap drops the oldest DOM but never its metadata.

Two constraints on the "warn when retained iframe resource use is high" improvement, both worth knowing before it gets scoped:

• There is no resource signal to threshold on. Nothing in lib/, the sidecar, or src-tauri reads memory today. The only in-page option, performance.measureUserAgentSpecificMemory(), needs cross-origin isolation and attributes cross-origin content in aggregate, so a per-iframe number is not reachable from the embedder anyway. A warning would be a count or age heuristic over parkedIds() unless the standalone host grows a process-memory read of its own — and that path doesn't exist in the VS Code host.
• The Baseboard notice is a single host-supplied slot. baseboardNotice is one opaque ReactNode threaded App → Wall → Baseboard, passed only by standalone/src/main.tsx for the updater; the VS Code host passes none. A lib-owned warning either contends with the updater notice for that slot or needs its own path — which also makes a per-Door indicator on the Baseboard the cheaper first version.