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.

.golangci.yml and the lint cleanup: #6

Model: opus-5-5

script/test

@@ -1,18 +1,23 @@
 #!/bin/sh
-# script/test: run the test suite. Quiet on success; on failure, rerun
-# verbosely for full diagnostic output (the exit 1 ensures the rerun
-# never turns a failure into a pass).
+# script/test: run the test suite. Testing is a phase of the Dockerfile
+# and this builds that phase alone, on the same terms as script/lint:
+# --target because a phase that is not the last stage is built only when
+# named, --no-cache because a cached test layer is a test that did not
+# run, and a tag so each build replaces the previous image.
 set -eu
 
-ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd -P)"
+ROOT="$(cd "$SCRIPT_DIR/.." && pwd -P)"
 
 main() {
     cd "$ROOT"
-    go test -race -timeout 30s ./... || {
-        echo "--- Rerunning with -v for details ---"
-        go test -race -timeout 30s -v ./...
-        exit 1
-    }
+    # The tag gets its own line: a failing command substitution inside
+    # an argument does not trip `set -e`, so the inline form degrades
+    # silently to an empty constant.
+    tag="$("$SCRIPT_DIR/projectname")"
+    docker build --no-cache \
+        --target test \
+        -t "$tag-test" .
 }
 
 main "$@"