chore: re-vendor canonical files from prompts at dd4027b (closes #472)

Copies .dockerignore, .gitignore, .prettierignore, check.yml and
REPO_POLICIES.md from sneak/prompts at dd4027b. The repo's own entries
(dist/, release/, yarn files) are kept after the canonical content.

The Dockerfile gets separate lint and test phases. Its last stage
depends on both, checks the git describe version and runs make build.
script/lint, test, check, cibuild and docker are the canonical models.
check-censored moves into the lint phase and test-verify-build into the
test phase. fmt and fmt-check fall back to the nvm-installed node. The
e2e image builds are uncached. Comments that cited the old test caps
now say 60 seconds, and comments that named what runs a script now name
the Dockerfile phase or stage.

Model: opus-5-5

.gitea/workflows/check.yml

@@ -3,9 +3,6 @@ on: [push]
 jobs:
     check:
         runs-on: ubuntu-latest
-        # Bounds script/cibuild, a cold-cache build included, so a hang frees
-        # the shared runner. README.md "In CI" has the measured times.
-        timeout-minutes: 10
         steps:
             # actions/checkout v4.2.2, 2026-02-22
             - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683

.gitea/workflows/e2e.yml

@@ -2,11 +2,11 @@ name: e2e
 on: [push]
 
 # The browser end-to-end suites, one job per browser, deliberately kept out
-# of the check workflow: REPO_POLICIES.md caps make test at 20 seconds and
-# script/cibuild is a plain `docker build .` whose Dockerfile runs
-# make check, so folding a browser suite into either would blow that cap
-# and slow the local fast path. Before this workflow every browser-level
-# guarantee in this repo held only when a human remembered to run it.
+# of the check workflow: REPO_POLICIES.md caps make test at 60 seconds and
+# script/cibuild runs make check, so folding a browser suite into either
+# would blow that cap and slow the local fast path. Before this workflow
+# every browser-level guarantee in this repo held only when a human
+# remembered to run it.
 #
 # One job per browser rather than two steps in one job, so a Chrome failure
 # does not hide the Firefox result.