fix(scope): close remaining ownership boundaries

docs/core-data-structures/tools.md

@@ -81,7 +81,7 @@ type InferArgs<S extends SchemaSpec> = Simplify<
 
 `defineTool({ name, description, parameters, execute, … })` ties it together: `parameters` is a `SchemaSpec`, `execute(args, exec)` gets `args: InferArgs<typeof parameters>`, and the helper converts the spec to JSON Schema (`schemaSpecToJsonSchema`) for the wire and validates model-generated args (`validateArgs`) before the typed body runs. A mismatch throws `ToolArgsError` (`code: 'INVALID_ARGS'`), which the registry turns into an `isError` result so the model can self-correct. Why a custom DSL and not schemastery: tool parameters need JSON Schema (the LLM wire format), not validation/transformation — the lightweight DSL gives the best authoring DX with the smallest surface.
 
-Registration is a value boundary. `ToolRegistry.register()` validates `ToolDefinition.parameters` as lossless JSON before and after cloning, copies the scalar fields, binds the execute/presentation callbacks once to the original definition as their method receiver, and deep-freezes the stored record. Replacing a callback property on the caller-owned definition later does not change dispatch. `get()`/`visible()` expose only that frozen snapshot, while `schemas()` produces detached projections, so the model-visible and executable views cannot drift through a leaked mutable registry object.
+Registration is a value boundary. `ToolRegistry.register()` reads every top-level field once, validates fixed scalar and callback types, materializes `ToolDefinition.parameters` as detached lossless JSON in one recursive pass, binds the accepted execute/presentation callbacks once to the original definition as their method receiver, and deep-freezes the stored record. Replacing a callback property on the caller-owned definition later does not change dispatch. `get()`/`visible()` expose only that frozen snapshot, while `schemas()` produces detached projections, so the model-visible and executable views cannot drift through a leaked mutable registry object.
 
 ## Execution: extensible waterfalls plus monotonic policy
 
@@ -118,7 +118,7 @@ interface ToolExecution extends ToolExecutionInput {
 }
 ```
 
-`ToolExecutionToken` is a compile-time opaque type and a frozen, property-free object at runtime; identity comparison is its only operation. Before policy runs, `ctx.tools.execute()` requires the caller's `arguments` to be losslessly JSON-serializable, checks again after cloning to contain unstable accessors, assigns a fresh token, and deep-freezes the detached arguments. A cloneable mutable exotic such as `Map` is rejected and normalized to an error before policy. `token`, `callId`, `name`, `arguments`, `agent`, and the optional `parent` token are non-writable throughout all waterfalls, so a listener cannot change which capability or scope was authorized or reach a live enclosing execution; an around-dispatch wrapper may add, replace, or remove only optional `signal`. After the complete pipeline the registry freezes the execution and exposes its stable identity to `tools/result` observers, where the execution remains usable as a `WeakMap` key without mutation races.
+`ToolExecutionToken` is a compile-time opaque type and a frozen, property-free object at runtime; identity comparison is its only operation. Before policy runs, `ctx.tools.execute()` reads each caller-owned field once, materializes `arguments` as detached lossless JSON in one recursive pass, assigns a fresh token, and deep-freezes the accepted arguments. A mutable exotic such as `Map` is rejected and normalized to an error before policy; one-pass materialization prevents a stateful getter from supplying different values to validation and storage. `token`, `callId`, `name`, `arguments`, `agent`, and the optional `parent` token are non-writable throughout all waterfalls, so a listener cannot change which capability or scope was authorized or reach a live enclosing execution; an around-dispatch wrapper may add, replace, or remove only optional `signal`. After the complete pipeline the registry freezes the execution and exposes its stable identity to `tools/result` observers, where the execution remains usable as a `WeakMap` key without mutation races.
 
 A `ToolGuard` is scope-aware final pre-dispatch policy. Its shape deliberately has no allow result: `undefined` preserves the waterfall decision, while a returned reason can only reduce permission, so a later listener cannot undo it.