test(cli): assert on runner-agnostic suffix of migrateNotImplemented

`migrateNotImplemented` was converted from a string to a runner-aware
factory in 6cc47d2; the existing E2E assertion still passed it as a
string to `toContain`, which then matched against the printed function
name instead of the warning text. Local unit tests use a separate
vitest config and didn't catch it; the CLI E2E job did.

Switch the assertion to the stable runner-agnostic suffix
`'stash db migrate" is not yet implemented.'` — works under any
runner the test environment detects (pnpm dlx in CI, npm/npx
locally).

Author: auxesis

packages/cli/tests/e2e/smoke.e2e.test.ts

@@ -69,6 +69,8 @@ describe('stash CLI — non-interactive smoke', () => {
     const r = render(['db', 'migrate'])
     const { exitCode } = await r.exit
     expect(exitCode).toBe(0)
-    expect(r.output).toContain(messages.db.migrateNotImplemented)
+    // `migrateNotImplemented` is a runner-aware factory; the runner-agnostic
+    // suffix is the stable assertion target.
+    expect(r.output).toContain('stash db migrate" is not yet implemented.')
   })
 })