Bring the repo up to the standard layout (closes #1)

Vendors .gitignore, .dockerignore, .editorconfig, REPO_POLICIES.md,
script/cibuild, script/docker, script/lint, script/test and the CI
workflow byte-identical from sneak/prompts commit cc440118c876; the
two ignore files then add this repo's own build output, root-anchored
so cmd/bsdaily/ stays in. The Dockerfile gains a lint phase on the
golangci-lint image already pinned and a test phase on the Debian Go
image with sqlite3 and zstd; the build stage copies a file from each,
so a plain docker build cannot skip them. Nothing installs
golangci-lint on the host. On apt, script/bootstrap refreshes the
package lists once before its first install.

.golangci.yml and the lint cleanup: #6

Model: opus-5-5

.gitea/workflows/check.yml

@@ -1,14 +1,9 @@
 name: check
-on:
-  push:
-    branches: [main]
-  pull_request:
-    branches: [main]
+on: [push]
 jobs:
-  check:
-    runs-on: ubuntu-latest
-    steps:
-      # actions/checkout v4, 2024-09-16
-      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5
-      - name: Build and check
-        run: script/cibuild
+    check:
+        runs-on: ubuntu-latest
+        steps:
+            # actions/checkout v4.2.2, 2026-02-22
+            - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683
+            - run: script/cibuild