feat(vnext): add disposable completion info (#200)

## Summary

- expose an opt-in, type-safe completion info resolver on the vNext
CodeMirror adapter
- give every resolver an AbortSignal and require explicit DOM resource
cleanup
- abort pending work and destroy resolved UI on option, document,
context, region, or view changes
- contain resolver/cleanup failures and reject cleanup reentrancy
- document the React-root integration pattern and export the public
resolver types

## Verification

- 43 test files; 2,036 passed and 1 expected failure
- changed coverage: 98.15% statements, 95.90% branches, 100% functions,
99.20% lines
- all strict/loose/demo TypeScript configurations pass
- oxlint and test-integrity checks pass
- build and runtime export smoke pass
- two independent exact-head adversarial reviews approve
`e07f8e525d6e6f2c7f73e24acd4e1f0b1ff90cc0`

Stacked on #199, now merged into `dev-refactor`.

<!-- This is an auto-generated description by cubic. -->
---
## Summary by cubic
Adds opt-in rich completion info to the vNext CodeMirror adapter.
Introduces a type-safe `infoResolver` that returns a disposable DOM
panel, with automatic abort and cleanup on selection or editor changes.

- **New Features**
- `autocomplete.infoResolver(item, { signal })` lets you render rich
info and return `{ dom, destroy }`; pending work is aborted and resolved
resources are destroyed on option selection changes,
document/context/region updates, or view disposal.
- Stale results are ignored; null results omit the panel; resolver and
cleanup failures are contained; reentrancy during cleanup is rejected.
- Docs updated with a React root example; exported
`SqlCompletionInfoResolver`, `SqlCompletionInfoResolverContext`, and
`SqlDisposableCompletionInfo` from `src/vnext/codemirror/index.ts`.

- **Migration**
  - Opt in by passing `sqlEditor({ autocomplete: { infoResolver } })`.
- Your resolver should use the provided `AbortSignal` and return `{ dom,
destroy }` or `null`.

<sup>Written for commit e07f8e5.
Summary will update on new commits.</sup>

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Author: Light2Dark

docs/vnext/codemirror-adapter.md

@@ -47,6 +47,29 @@ The adapter installs one coherent `autocompletion` configuration. Additional
 sources belong in `autocomplete.externalSources`; consumers should not install
 a second independently configured `autocompletion` extension.
 
+Rich completion details are opt-in through
+`autocomplete.infoResolver`. The resolver receives the immutable core item and
+an `AbortSignal`, and returns a DOM resource with an explicit `destroy`
+callback. The adapter aborts pending work and destroys resolved resources when
+the selected option, document input, context, regions, or view lifetime
+changes. Resolver failures are contained and simply omit the detail panel.
+
+```ts
+const support = sqlEditor({
+  autocomplete: {
+    infoResolver: async (item, { signal }) => {
+      const metadata = await loadMetadata(item, { signal });
+      const dom = document.createElement("div");
+      const root = createRoot(dom);
+      root.render(renderMetadata(metadata));
+      return { dom, destroy: () => root.unmount() };
+    },
+  },
+  initialContext,
+  service,
+});
+```
+
 ## Atomic inputs
 
 Context and document changes can share one CodeMirror transaction: