Current templates: safe.directory, golangci-lint v2.14.0, fetch-depth 0, the policy's last stage (closes #50)

REPO_POLICIES.md and .golangci.yml are the sneak/prompts next copies, and
.dockerignore takes the template's .git/modules/**/config line. The lint
phase runs golangci-lint v2.14.0; its two errors.AsType findings are
fixed. The stage that builds keyfunc marks /src safe for git, so a
context sent as a tar stream still yields a version. That stage is now
the last one and a development environment on the Debian Go image: what
script/bootstrap installs, the source in /src, keyfunc on the PATH. The
test phase uses the same image, so one Go image stays matched to
script/bootstrap. The CI checkout fetches all history and tags.

Model: opus-5-5

README.md

@@ -331,7 +331,10 @@ standard: most Makefile targets are thin shims over an executable in `script/`
 - `script/docker` builds the Docker image, uncached, tagged with the project
   name and stamped with the version `git describe` gives on the host. The image
   cannot be built unless the `lint` and `test` phases pass, so a plain
-  `docker build .` runs them too.
+  `docker build .` runs them too. The image is a development environment, not a
+  runtime image: the Debian Go image with what `script/bootstrap` installs, the
+  source tree in `/src`, and `keyfunc` built from it on the `PATH`.
+  `docker run --rm -it keyfunc` opens a shell in it.
 - `script/cibuild` is the CI build the Gitea workflow calls: it runs
   `bootstrap`, then `check`, then builds the image as `script/docker` does.
 - `script/precommit` is what the git pre-commit hook runs: `go mod tidy` and