Add test requirements to checklists, .dockerignore URLs, root symlink, and Makefile comment

- Add test requirement item to both checklists (must not be a no-op)
- Add .dockerignore template URL to Dockerfile items in both checklists
- Add REPO_POLICIES.md symlink in repo root pointing to prompts/
- Add comment to Makefile explaining why prettier flags are repeated

prompts/NEW_REPO_CHECKLIST.md

@@ -50,7 +50,8 @@ Template files can be fetched from:
 - [ ] `LICENSE` file matching the chosen license
 - [ ] `REPO_POLICIES.md` — fetch from
       `https://git.eeqj.de/sneak/prompts/raw/branch/main/prompts/REPO_POLICIES.md`
-- [ ] `Dockerfile` and `.dockerignore`
+- [ ] `Dockerfile` and `.dockerignore` — fetch `.dockerignore` from
+      `https://git.eeqj.de/sneak/prompts/raw/branch/main/.dockerignore`
     - All Dockerfiles must run `make check` as a build step
     - Server: also builds and runs the application
     - Non-server: brings up dev environment and runs `make check`
@@ -66,7 +67,7 @@ Template files can be fetched from:
 
 ## Configure Makefile
 
-- [ ] `make test` — runs project tests (30-second timeout)
+- [ ] `make test` — runs real tests, not a no-op (30-second timeout)
 - [ ] `make lint` — runs linter
 - [ ] `make fmt` — formats code (writes)
 - [ ] `make fmt-check` — checks formatting (read-only)