docs: update CI testing docs for matrix unit workflow

AGENTS.md

@@ -190,13 +190,14 @@ packages/core/src/
 
 ### CI/CD Integration
 
-- GitHub Actions runs `yarn install` and `yarn test`
+- GitHub Actions unit tests run in `.github/workflows/test-unit.yml` as a matrix (`core`, `web`, `backend`, `scripts`) using `yarn test <project>` on `push`.
+- End-to-end tests run separately in `.github/workflows/test-e2e.yml` on pull requests to `main`.
 
 ## Troubleshooting
 
 ### Common Issues
 
-- **Test failures**: Run `yarn test:core`, `yarn test:web`, and `yarn test:backend` individually to narrow the scope of the failure
+- **Test failures**: Run `yarn test:core`, `yarn test:web`, `yarn test:backend`, and `yarn test:scripts` individually to narrow the scope of the failure
 - **Backend won't start**: Missing environment variables in `packages/backend/.env`, use web-only development (`yarn dev:web`)
 - Environment: Copy from `packages/backend/.env.local.example` to `packages/backend/.env` (there is no `.env.example`).
 - Webpack dev server warns about a missing `.env.local` file; this is harmless—it falls back to `process.env`.

docs/agent-onboarding.md

@@ -79,5 +79,6 @@ Run the smallest relevant checks first:
 - Core-only changes: `yarn test:core`
 - Web-only changes: `yarn test:web`
 - Backend-only changes: `yarn test:backend`
+- Scripts-only changes: `yarn test:scripts`
 - Cross-package type changes: `yarn test:core && yarn test:web && yarn test:backend`
 - Before handoff: `yarn type-check`

docs/testing-playbook.md

@@ -16,6 +16,34 @@ yarn type-check
 
 Avoid defaulting to `yarn test` unless you really need the full suite.
 
+## CI Unit Test Workflow
+
+Source of truth:
+
+- `.github/workflows/test-unit.yml`
+- `.github/workflows/test-e2e.yml`
+
+Unit workflow (`test-unit.yml`):
+
+- triggers on `push`
+- runs a matrix across `core`, `web`, `backend`, and `scripts`
+- uses `fail-fast: false`, so one failing lane does not cancel the others
+- runs `yarn test <project>` in each lane after dependency install
+- passes timezone through `TZ: ${{ vars.TZ }}`
+
+Local parity commands:
+
+```bash
+yarn test core
+yarn test web
+yarn test backend
+yarn test scripts
+```
+
+`yarn test:<project>` aliases are equivalent and usually easier to remember.
+
+E2E workflow (`test-e2e.yml`) is separate and runs on pull requests to `main` via `yarn test:e2e`.
+
 ## Jest Project Layout
 
 Source: