fix(scope): detach drained entry generations

.agents/notes/implemented/architecture/2026-07-12-scoped-layers-store.md

@@ -74,17 +74,17 @@ export class AnonymousEntries<V> {
 
 - The constructor creates `global` once with `createLayer(undefined)`. A scoped layer is created only by `effect()`; `peek()` and `merge()` never create one, and `peek(undefined)` returns `undefined` because the global layer is already explicit.
 - `merge()` is the only materialized generic read. It copies named global entries in insertion order, then applies matching scoped entries in their insertion order so same-name entries shadow without moving unrelated names.
-- `NamedEntries.insert()` checks and inserts atomically, returns an idempotent exact-entry undo, and obtains the registry's exact duplicate diagnostic from the caller-supplied factory. Lookup and iterators retain native `Map` order and live iteration.
-- `AnonymousEntries.append()` assigns a unique internal key per registration, so equal callbacks or values remain independent. Its iterator is live and insertion-ordered.
+- `NamedEntries.insert()` checks and inserts atomically, returns an idempotent exact-entry undo, and obtains the registry's exact duplicate diagnostic from the caller-supplied factory. Lookup and iterators retain native `Map` order and stay live within one nonempty table generation; draining the table starts a new generation so an in-flight iterator cannot observe a self-replacement.
+- `AnonymousEntries.append()` assigns a unique internal key per registration, so equal callbacks or values remain independent. Its iterator is insertion-ordered and uses the same live-generation boundary.
 - `effect()` derives the key with `scopeOf(ctx)` and attaches the action to that same `ctx.effect()`. It accepts one synchronous action returning one synchronous undo; actions must either return their undo or throw before retaining a contribution. The helper does not normalize the wider Cordis `Effect` union.
 - `effect()` collects the action's undo before calling `onChange` and returns the exact `ctx.effect()` disposer. Disposal runs the action undo before notification, is idempotent through Cordis, and removes a scoped layer only after its complete `ScopeLayer.isEmpty()` becomes true.
 - `options.notify` defaults to `true`. The callback's own policy stays authoritative: tool and prompt change callbacks may throw and trigger registration rollback; `CommandService.notifyChange()` contains observer failures; tool guards pass `notify: false`.
 
 ## Registry migrations
 
-`dsh-tools` defines one `ToolLayer` containing named tools plus anonymous compiled restrictions and guard registrations. `ToolRegistry` retains its private domain resolver for visible definitions, pre-restriction known names, restrictable global names, scoped shadowing, restrictions, and reserved `run_code` insertion. Guard evaluation continues to live-iterate global then scoped registrations so re-entrant additions retain current behavior.
+`dsh-tools` defines one `ToolLayer` containing named tools plus anonymous compiled restrictions and guard registrations. `ToolRegistry` retains its private domain resolver for visible definitions, pre-restriction known names, restrictable global names, scoped shadowing, restrictions, and reserved `run_code` insertion. Guard evaluation live-iterates global then scoped registrations: additions to a nonempty generation can run in the current dispatch, while a self-replacement after draining the guard table begins with the next dispatch.
 
-`dsh-system-prompt` defines one `PromptLayer` containing named sections and variables plus anonymous tool providers. Assembly merges sections before evaluating them, so a shadowed provider is never called. Tool-provider membership is materialized once per assembly. Variable providers continue to live-iterate global then scoped tables, preserving re-entrant registration behavior.
+`dsh-system-prompt` defines one `PromptLayer` containing named sections and variables plus anonymous tool providers. Assembly merges sections before evaluating them, so a shadowed provider is never called. Tool-provider membership is materialized once per assembly. Variable providers live-iterate global then scoped tables: additions to a nonempty generation can run in the current assembly, while a self-replacement after draining the variable table begins with the next assembly.
 
 `dsh-commands` defines a one-table layer containing `NamedEntries<RegisteredCommand>`. Effective views use `merge()`, while `CommandService` retains definition normalization and freezing, exact duplicate diagnostics, sorted immutable descriptors, direct execution, HMR cleanup, and independently contained `commands/change` observers.
 
@@ -120,7 +120,7 @@ All seven facades keep validation and diagnostics in their owning registry and c
 
 ## Verification
 
-- `dsh-scope` unit tests cover global construction, lazy scoped construction, non-creating reads, named merge order and shadowing, aggregate reclamation, factory and action failure cleanup, notification ordering and rollback, `notify: false`, effect labels, exact disposer identity, idempotent teardown, caller-owned duplicate errors, independent anonymous duplicates, and live iterators.
-- Focused tool, system-prompt, and command suites cover restrictions, reserved transport handling, known/restrictable-name agreement, guard re-entrancy, validation order, exact diagnostics, section shadow-before-evaluate, provider snapshot membership, variable re-entrancy, contained command observers, frozen and sorted views, direct execution, and lifecycle disposal.
+- `dsh-scope` unit tests cover global construction, lazy scoped construction, non-creating reads, named merge order and shadowing, aggregate reclamation, factory and action failure cleanup, notification ordering and rollback, `notify: false`, effect labels, exact disposer identity, idempotent teardown, caller-owned duplicate errors, independent anonymous duplicates, live iterators, and drained-generation detachment.
+- Focused tool, system-prompt, and command suites cover restrictions, reserved transport handling, known/restrictable-name agreement, guard re-entrancy and self-replacement, validation order, exact diagnostics, section shadow-before-evaluate, provider snapshot membership, variable re-entrancy and self-replacement, contained command observers, frozen and sorted views, direct execution, and lifecycle disposal.
 - The scoped core-data type-equivalence check ties `ScopeLayer` documentation to its source declaration. Repository documentation, module-graph, build, hygiene, coverage, and built-artifact gates exercise the root export and package boundary.
 - Existing ACP, headless, and TUI keyless snapshots remain the regression boundary for tool schemas, prompt assembly, and human commands. The implementation does not update any expected transcript.