refactor(tools): move render-intent vocabulary to presentation.ts

The tool render-intent vocabulary (ToolCallView/ToolResultView + members,
FileLocation, FileDiff, ToolCallKind) is the UI-facing surface of
dsh-tools; it lived inline in index.ts alongside the registry and
execution core. Move it to its own presentation.ts module so index.ts is
the registry + execute waterfall and the presentation vocabulary is a
separate, one-directional dependency.

presentation.ts owns ONLY render-intent types and references none of the
execution types; index.ts imports the view types for ToolDefinition's
presentCall/presentResult signatures (clean acyclic index -> presentation).
The opaque `meta` presentation channel (ToolExecuteReturn, ToolResult,
ToolExecutionResult) is execution plumbing and stays in index.ts.

Public surface unchanged: index.ts re-exports the vocabulary, so consumers
(tool-fs/tool-bash/tool-web/tool-todo, the ACP bridge) keep importing from
@deepseek-ai/dsh-tools with zero churn. No producer/bridge/test edits; a
pure internal relocation with no observable-output change (snapshot goldens
untouched).

packages/core/tools/src/schema.ts

@@ -20,7 +20,8 @@
  */
 
 import { assertNever, HarnessError } from '@deepseek-ai/dsh-llm'
-import type { ToolCallView, ToolDefinition, ToolExecuteReturn, ToolExecution, ToolResult, ToolResultView } from './index.ts'
+import type { ToolDefinition, ToolExecuteReturn, ToolExecution, ToolResult } from './index.ts'
+import type { ToolCallView, ToolResultView } from './presentation.ts'
 
 // ---------------------------------------------------------------------------
 // SchemaSpec — the author-facing per-property type