fix(tool-tasks): claim completion notices only for the mount's own scope

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

.agents/notes/implemented/architecture/2026-08-08-per-preset-standing-mounts.i18n.yaml

@@ -2,5 +2,5 @@
 # side as of the last confirmed-consistent state. Both languages carry equal authority;
 # after editing either side, bring the other along and re-record with:
 #   pnpm run verify-translation-pairing --write .agents/notes/implemented/architecture/2026-08-08-per-preset-standing-mounts.md
-2026-08-08-per-preset-standing-mounts.md: 834d645f5f293a2e137b8faf662e301f1e8bb971
-2026-08-08-per-preset-standing-mounts.zh.md: 45ce0f4e7dec28e5bf807898dc9cdbf32b8e4eb5
+2026-08-08-per-preset-standing-mounts.md: c2792454f90a88cd6fba36eed8e36104e5fffea4
+2026-08-08-per-preset-standing-mounts.zh.md: 47668c8c2c424eb188aa14bf55986d27bcfb8ee0

.agents/notes/implemented/architecture/2026-08-08-per-preset-standing-mounts.md

@@ -16,7 +16,7 @@ A preset is one composition per PROCESS, not one per session. The roster mounts
 
 Standing mounts fix the class, not the instances: the registrations a reader needs exist for the process lifetime, keyed by preset id, no agent required. What made it cheap
 
-- The stateful preset plugins (`plan-mode`, `token-meter`, `compact-basic`, `tasks-local`) already key state by `Session`/`Agent` — they predate presets. Sharing one instance is a return to their design, not a rewrite.
+- The stateful preset plugins (`plan-mode`, `token-meter`, `compact-basic`) already key state by `Session`/`Agent` — they predate presets. Sharing one instance is a return to their design, not a rewrite. `tasks-local` shared that property and has since left the preset plane entirely: producers outside its realm (`tool-bash`, `tool-pty`, a non-continuable `tool-subagent`) resolve the registry with `ctx.get`, which an entry-local realm hides from them, so it is composed on the host plane and only the model-facing `tool-tasks` row stays per preset.
 - Preset ymls are unchanged: one mount per preset = one Entry per preset, whose entry-local realms (`isolate: <name>: true`) keep two presets' same-named services apart exactly as they kept two sessions' apart.
 - A shared realm label was NOT an option: `provide()` throws on a second registration under the same realm symbol, so labels pool the REALM, never the instance — a per-session world sharing a label crashes the second mount.
 

.agents/notes/implemented/architecture/2026-08-08-per-preset-standing-mounts.zh.md

@@ -16,7 +16,7 @@ Status: implemented
 
 常驻挂载修的是这一类问题而非其中的个例：读取方需要的注册在进程生命周期内始终存在，按 preset id 索引，不需要任何 agent。让它便宜的原因：
 
-- 有状态的 preset 插件（`plan-mode`、`token-meter`、`compact-basic`、`tasks-local`）本就按 `Session`/`Agent` 分键存状态——它们早于 preset 存在。共享一份实例是回归其设计，不是改写。
+- 有状态的 preset 插件（`plan-mode`、`token-meter`、`compact-basic`）本就按 `Session`/`Agent` 分键存状态——它们早于 preset 存在。共享一份实例是回归其设计，不是改写。`tasks-local` 同样具备该性质，且此后已完全离开 preset 平面：realm 之外的生产方（`tool-bash`、`tool-pty`、非 continuable 的 `tool-subagent`）以 `ctx.get` 解析该注册表，而 entry-local realm 对它们不可见，因此它组合在宿主平面，只有面向模型的 `tool-tasks` 行仍留在各 preset 中。
 - preset 的 yml 不变：每 preset 挂一次 = 每 preset 一个 Entry，其 entry 本地 realm（`isolate: <name>: true`）让两个 preset 的同名服务互不相干，正如它从前隔开两个会话。
 - 共享 realm label **不是**选项：`provide()` 对同一 realm 符号下的第二次注册直接抛错，label 池化的是 REALM 而非实例——按会话挂载的世界里共享 label 会让第二次挂载崩溃。