feat(opencode): add tool metadata buffering and migrate virtua to v0.42.3

Introduce a `metadata` method on SessionProcessor.Handle that buffers
metadata emitted before tool-call registration, then applies it on the
running transition. This decouples metadata emission timing from
tool-call lifecycle.

Downgrade virtua from 0.49.1 to 0.42.3 and migrate the virtualizer API:
- Replace `findItemIndex(scrollOffset)` with `findStartIndex()`
- Replace `bufferSize` prop with `overscan` (count-based)

Additional changes:
- Change Permission.reply return type from Promise<boolean> to Promise<void>
- Make Ruleset type readonly and remove unnecessary array spreads
- Update nvidia provider headers to reference Kilo branding
- Reorder SDK event type definitions for installation events
- Reduce promise facade allowlist in check script

packages/opencode/test/session/compaction.test.ts

@@ -203,6 +203,7 @@ function fake(
       return msg
     },
     updateToolCall: Effect.fn("TestSessionProcessor.updateToolCall")(() => Effect.succeed(undefined)),
+    metadata: Effect.fn("TestSessionProcessor.metadata")(() => Effect.void), // kilocode_change
     completeToolCall: Effect.fn("TestSessionProcessor.completeToolCall")(() => Effect.void),
     process: Effect.fn("TestSessionProcessor.process")(() => Effect.succeed(result)),
   } satisfies SessionProcessorModule.SessionProcessor.Handle