Re-vendor the standard files from sneak/prompts dd4027b (closes #33)

REPO_POLICIES.md, .golangci.yml, the CI workflow and the scripts the
policy keeps identical across repositories are copies of the files at
that commit. .gitignore, .editorconfig and the new .dockerignore are the
canonical files followed by this repository's own entries. The lint
stage moves to the golangci-lint image the policy pins, in the same
commit as .golangci.yml. The format check leaves the lint stage and runs
on the host from script/check, which script/cibuild now runs after
script/bootstrap. The last Dockerfile stage runs script/bootstrap.
script/fmt runs goimports with go run at a pinned commit.

Model: opus-5-5

TODO.md

@@ -17,13 +17,19 @@ maintenance; the library is referenced by the Go styleguide.
 
 # Next Step
 
-Bring the Makefile up to policy in one commit: add fmt-check, check, and
-hooks targets (test/lint/fmt/docker exist) and add the missing policy
-files it depends on: .golangci.yml, REPO_POLICIES.md, .editorconfig,
-.dockerignore, and .gitea/workflows/check.yml running make check.
+Restructure README.md into the standard sections: Description, Getting
+Started, Rationale, Design, TODO, License, Author
 
 # Completed Steps
 
+* 2026-10-06: re-vendored the standard files from `sneak/prompts` at
+    commit `dd4027b`: `REPO_POLICIES.md`, the CI workflow, `.gitignore`,
+    and `.golangci.yml` together with the lint stage's new image, plus
+    the `.editorconfig` and `.dockerignore` this repo lacked, which
+    finishes the Makefile and policy-files step. `script/cibuild` now
+    bootstraps and runs `script/check` before building the image, the
+    format check runs only on the host, the last `Dockerfile` stage runs
+    `script/bootstrap`, and `script/fmt` runs goimports at a pinned commit
 * 2026-10-06: the console handler takes the file and line it prints from
     the record's `PC` instead of counting stack frames, so they name the
     call site whether the record came through a `slog.Logger` or straight
@@ -63,8 +69,6 @@ files it depends on: .golangci.yml, REPO_POLICIES.md, .editorconfig,
 
 # Future Steps
 
-* Restructure README.md into the standard sections: Description,
-    Getting Started, Rationale, Design, TODO, License, Author
 * Delete the old plain TODO file once this TODO.md lands
 * Add .aider.* to .gitignore and remove the stray aider artifacts from
     the working tree