chore: relax the AGENTS.md test placement rule

Agent instructions (AGENTS.md and the test-writing guide) now say webapp
tests go in `apps/webapp/test/`, and packages follow their existing
layout (next to the source or in a `test/` folder).

Mono-RevId: 3ac9cac75ceaff967dc461f695192cdef33fef87

Author: ericallam

AGENTS.md

@@ -51,7 +51,10 @@ pnpm run test ./src/engine/tests/ttl.test.ts --run     # Single test file
 pnpm run build --filter @internal/run-engine           # May need to build deps first
 ```
 
-Test files go next to source files (e.g., `MyService.ts` -> `MyService.test.ts`).
+Where test files go:
+
+- **Webapp:** put tests in `apps/webapp/test/`, not next to the source. Vitest there only runs files matched by the `include` list in `apps/webapp/vitest.config.ts`.
+- **Packages:** follow the package's existing layout. Next to the source (`MyService.ts` -> `MyService.test.ts`) and a `test/` folder are both fine.
 
 ### Testcontainers for Redis/PostgreSQL
 

ai/references/tests.md

@@ -10,25 +10,25 @@ Prefer running tests on a single file (and first cding into the directory):
 
 ```bash
 cd apps/webapp
-pnpm run test ./src/components/Button.test.ts
+pnpm run test ./test/myService.test.ts
 ```
 
 If you are cd'ing into a directory, you may have to build dependencies first:
 
 ```bash
 pnpm run build --filter webapp
 cd apps/webapp
-pnpm run test ./src/components/Button.test.ts
+pnpm run test ./test/myService.test.ts
 ```
 
 ## Writing Tests
 
 We use vitest for testing. We almost NEVER mock anything. Start with a top-level "describe", and have multiple "it" statements inside of it.
 
-New test files should be placed right next to the file being tested. For example:
+Where new test files go:
 
-- Source file: `./src/services/MyService.ts`
-- Test file: `./src/services/MyService.test.ts`
+- Webapp: in `apps/webapp/test/`, not next to the source. Vitest there only runs files matched by the `include` list in `apps/webapp/vitest.config.ts`.
+- Packages: follow the package's existing layout. Next to the source (`./src/services/MyService.ts` -> `./src/services/MyService.test.ts`) and a `test/` folder are both fine.
 
 When writing anything that needs redis or postgresql, we have some internal "testcontainers" that are used to spin up a local instance, redis, or both.