The assembled Web snapshot lane selected its locale with a `dsh.locale`
localStorage key. That key stopped selecting anything once the locale
preference moved to the Host settings document, so the image-display
scenario's Chinese expectations met the English default and failed.
Pin the navigator languages the boot env already documents, and state the
image-display expectations in the lane's English copy — the fixture session
title stays Chinese because it is fixture data, not product copy.
`ScopedLayers.effect` already returns an exact `() => void`, so the inherited
`() => void dispose()` wrapper voided a void — two lint rules, four errors.
The scoped layer's own teardown had no test, which is the registry-contribution
disposal contract the testing policy requires and the only path that calls
`TaskLayer.isEmpty()`: `ScopedLayers` prunes a scope's layer when its last
contribution disposes. The new case mounts one plugin contributing both a
surface and a listener into one scope, then unloads it and observes that the
agents which joined that scope are refused again.
Refs #2141
One host registry serves every composition in the process, so its two
service-wide collections answered per-owner questions process-wide. `start()`
asked only whether SOME surface was attached, so an agent whose own composition
loads no `tool-tasks` could start work it has no tool to collect or stop as soon
as any other preset attached one — and the answer changed depending on which
sessions happened to be open. `settle()` walked every registered listener, so a
task settling without a waiter injected one completion notice per mounted
preset into the same owner.
Both collections now sit in `ScopedLayers`, the layered-registry primitive
`tools` and `skills` already use: a registration files into its registering
context's scope, and a read unions the global layer with the owner's scope
chain. A surface or listener registered from an unscoped context lands in the
global layer and serves every owner, which is exactly the host-plane
composition's own controls, so the TUI path is unchanged without a special
case.
This supersedes the consumer-side filter in the previous commit. That filter
produced the right notices but sat in the wrong layer: it left the `start()`
gate process-wide, it could not be enforced against a producer that resolves
the registry directly, and it made a Consumer carry scope knowledge that the
other layered registries keep in the registry. `tool-tasks` is scope-agnostic
again and the `dsh-scope` edge moves to `tasks-local`.
`start()`'s refusal is now owner-relative, so its model-visible text names the
agent rather than the process. The shipped `minimal` preset keeps
`enableRunInBackground: false`, no longer as the safety boundary — the registry
owns that now — but so an agent that could never collect a task is not offered
the parameter at all.
Refs #2141
Moving the task registry to the host plane put every preset's `tool-tasks`
listener on ONE `LocalTaskService`. `settle()` computes a single snapshot and
walks every registered listener with no scope filter, and it marks `reported`
only when a waiter is present — so a task settling without a waiter reached
each mount's listener with `reported` false and every one of them injected the
same completion into the same owner. Three shipped presets carry `tool-tasks`,
and a preset file edit adds a second generation of the same mount, so an agent
read N copies of one notice as model-visible durable context.
A mount now claims an owner only when the owner's scope chain reaches the
mount's own scope. An unscoped mount is the host-plane instance that serves
every agent, which keeps the TUI composition and every existing test intact.
Registry-side ownership was the alternative: mark `reported` once the first
listener claims it. It is wrong because `onTaskDone` is not a notice-only
seam — the `dsh-tasks` invariant companion registers a validating listener —
so first-claim-wins would silence observers that are not delivering anything.
The regression test mounts two scoped `tool-tasks` over one registry and
settles an unowned-wait task, which is the only path that reaches the notice
listeners at all: the shipped-composition e2e uses `wait: true`, and a waiter
marks `reported` before settlement, so that test structurally cannot cover it.
Also corrects the standing-mounts Agent Note, which still listed `tasks-local`
among the stateful PRESET plugins.
Refs #2141
