chore: repo policy compliance sweep — test rerun, npx, frozen lockfile, docs (closes #166)

- script/test runs the suite quietly, then reruns it with --verbose on
  failure and always exits 1 (REPO_POLICIES.md conditional verbose rerun
  pattern). New package.json script test:verbose is the -v form of the
  existing jest --forceExit invocation.
- build.js calls node_modules/.bin/tailwindcss instead of npx, which
  would fetch from the registry unpinned if the binary were absent.
- make install uses --frozen-lockfile, so a stale yarn.lock fails the
  target instead of being silently rewritten.
- README Getting Started uses make setup (which also installs the
  pre-commit hook); the Makefile-only targets (install, hooks, build,
  build-debug, clean, dev) are now documented in Entrypoints.
- .dockerignore records why .git is deliberately not excluded.

README.md

@@ -31,10 +31,13 @@ list exists to detect symbol spoofing attacks and improve UX.
 ```bash
 git clone https://git.eeqj.de/sneak/autistmask.git
 cd autistmask
-make install
+make setup
 make build
 ```
 
+`make setup` is the entrypoint for a fresh clone: it installs dependencies from
+the lockfile and installs the git pre-commit hook.
+
 Load the extension:
 
 - **Chrome**: Navigate to `chrome://extensions/`, enable "Developer mode", click
@@ -97,6 +100,19 @@ provide:
 - `script/precommit` — run by the git pre-commit hook; runs `script/check`
 - `script/install-precommit` — install the git pre-commit hook
 
+The Makefile shims to those. It also carries a few targets that have no
+`script/` counterpart and are Makefile-only conveniences:
+
+- `make install` — `yarn install --frozen-lockfile` on its own, without the rest
+  of `script/bootstrap`. Frozen so a stale `yarn.lock` fails instead of being
+  silently rewritten. Use `make setup` for a fresh clone.
+- `make hooks` — shims to `script/install-precommit`
+- `make build` — build the extension into `dist/chrome/` and `dist/firefox/`
+- `make build-debug` — the same build with `AUTISTMASK_DEBUG=1` (see
+  [Debug Builds](#debug-builds))
+- `make clean` — remove `dist/`
+- `make dev` — build in watch mode
+
 ## End-to-End Tests
 
 `make test-e2e` builds `dist/chrome/` and drives the **real popup in a real