test(genbi): give the cache-key case a timeout, and name the generator prerequisite

The cache-key case runs three sequential compiles, each spawning subprocesses,
and does not fit vitest's 5s default: it timed out on one full-suite run and
passed in isolation at 732ms. It is the single test carrying the guarantee that
a changed generator misses the cache, so a timeout there reads as a cache
regression rather than a scheduling artifact — the most misleading way for this
change to fail.

The docs owed two things the implementation now assumes. RUNNING.md never named
the generator as a prerequisite, so following it to boot the BFF hit a loud
failure with no prior instruction. And the generator's identity is memoized per
path for the process lifetime, so a running BFF does not notice a rebuild at the
same path — worth stating where the rebuild is documented, since unlike the
pinned Warble package this binary is expected to be rebuilt during development.

apps/genbi/MAINTAINING.md

@@ -88,6 +88,13 @@ Both are committed so a profile compiles standalone for CI and dev, pinned to th
 `examples/v5-jaffle`. At run time the host regenerates the document against the user's real project
 and rewrites `project:` (see `composeUserProfile`); nothing at run time reads the committed copies.
 
+The generator's content hash is memoized per resolved path for the lifetime of the process, so a
+**running** BFF does not notice a generator rebuilt at the same path: the cache key does not move
+and a bundle compiled from the previous projection keeps being served. Restart the BFF after
+rebuilding the generator. This inherits from `warbleIdentity`, but bites harder here — Warble
+arrives pinned from npm, whereas this generator is an in-repo Rust build that is expected to be
+rebuilt during development.
+
 Regenerate them, from the repository root, in this order — the golden is compiled *from* the
 document, so a stale document silently produces a stale golden:
 

apps/genbi/RUNNING.md

@@ -22,6 +22,13 @@ Beyond the prerequisites in [README.md](./README.md#prerequisites):
   local and gateway runtimes are not accepted. Claude is by far the better
   exercised of the two — see [Codex status](#codex-status).
 - The Wren CLI on `PATH`:
+- **The `wren-context-loader` generator, built from this repo.** Binding a user's project
+  compiles a prepared-context document first, and the generator is a Rust binary rather than an
+  npm dependency, so `pnpm install` does not supply it. Build it once with
+  `cargo build --release --manifest-path core/wren-context-loader/Cargo.toml`, or point
+  `WREN_HARNESS_CONTEXT_LOADER_BIN` at an existing build. Without either, the first user-project
+  bind fails loudly — by design, since a silent fallback would leave no way to tell which path
+  produced an IR.
 
   ```bash
   uv tool install wrenai

apps/genbi/test/compile-context-loader.test.ts

@@ -164,5 +164,5 @@ describe("compile cache key vs a generator change (project held constant)", () =
     expect(keyA?.profileHash).toBe(keyB?.profileHash);
     expect(keyA?.warbleIdentity).toBe(keyB?.warbleIdentity);
     expect(keyA?.hubDir).toBe(keyB?.hubDir);
-  });
+  }, 30_000);
 });