test: snapshot-tool-race.test.ts throws Unbound layer node: LocationServiceMap #194

Split out from #181, whose "Unbound layer node" half turned out to be an unrelated root cause from the InterruptError half tracked there (confirmed: this reproduces 100% deterministically in isolation, not intermittently — see analysis below), so keeping both under one issue was misleading.

What's broken

`packages/opencode/test/session/snapshot-tool-race.test.ts` builds its Effect layer graph with the raw `LayerNode.compile(root, replacements)`. `Session.node` (part of `root`) depends on `LocationServiceMap.node`, and this file's replacement list never supplies it — so compiling the layer graph throws:

```
error: Unbound layer node: @opencode/example/LocationServiceMap
at packages/core/src/effect/layer-node.ts:260:48
```

Every other test file that pulls in `Session.node` (`session.test.ts`, `compaction.test.ts`, etc.) uses `AppNodeBuilder.build` instead, which auto-injects a `LocationServiceMap` replacement whenever the graph has an unbound dependency on it. This file was the one outlier still calling `LayerNode.compile` directly.

This reproduces deterministically on every single run of the file in isolation (the layer graph is built synchronously at module load) — not just during CI's `--only-failures` isolated rerun as originally suspected in #181.

Fix

Closes via #190 — switches to `AppNodeBuilder.build`, same pattern as the rest of the suite.