Set the lint digest and .golangci.yml together; state the Go version rule

The canonical .golangci.yml now names exhaustruct_v5, which v2.12.2
rejects, so a repo that re-vendors the file on the old digest gets a
lint phase that fails before checking any code. REPO_POLICIES now says
a repo sets the lint phase digest and re-vendors .golangci.yml in one
commit, whichever prompted the change, and both repo checklists point
to that rule. It also replaces "a new Go version needs a golangci-lint
built with it" with the rule golangci-lint applies: the go directive
must not name a newer Go minor version than the one it was built with.

Model: opus-5-5

TODO.md

@@ -25,7 +25,9 @@ fmt-check, and commit.
   because v2.12.2 refuses to lint a module whose `go` directive is 1.27 (issue
   65). Releases from v2.13.0 deprecate `exhaustruct` in favour of
   `exhaustruct_v5`, which `default: all` switches on, so the canonical
-  `.golangci.yml` now disables `exhaustruct_v5` beside `exhaustruct`.
+  `.golangci.yml` now disables `exhaustruct_v5` beside `exhaustruct`. v2.12.2
+  rejects that file, so `REPO_POLICIES.md` and both repo checklists now say a
+  repo sets the lint phase digest and re-vendors `.golangci.yml` in one commit.
 - 2026-10-03: Brought the canonical `.gitignore` level with `.dockerignore` on
   secrets (issue 38): it now also ignores `prod.env`-style `*.env` files,
   `.envrc`, `*.p12`, `*.pfx` and the extensionless SSH private keys, written to

prompts/EXISTING_REPO_CHECKLIST.md

@@ -1,6 +1,6 @@
 ---
 title: Existing Repo Checklist
-last_modified: 2026-10-02
+last_modified: 2026-10-03
 ---
 
 Use this checklist when beginning work in a repo that may not yet conform to our
@@ -80,7 +80,9 @@ with your task.
       `https://git.eeqj.de/sneak/prompts/raw/branch/main/.gitea/workflows/check.yml`
 - [ ] Language-specific config:
     - [ ] Go: `go.mod`, `go.sum`, `.golangci.yml` (fetch from
-          `https://git.eeqj.de/sneak/prompts/raw/branch/main/.golangci.yml`)
+          `https://git.eeqj.de/sneak/prompts/raw/branch/main/.golangci.yml` and,
+          in the same commit, set the lint phase digest to the one named in the
+          `.golangci.yml` paragraph of `REPO_POLICIES.md`)
     - [ ] JS: `package.json`, `yarn.lock`, `.prettierrc`, `.prettierignore`
           (fetch from
           `https://git.eeqj.de/sneak/prompts/raw/branch/main/.prettierrc` and

prompts/NEW_REPO_CHECKLIST.md

@@ -1,6 +1,6 @@
 ---
 title: New Repo Checklist
-last_modified: 2026-10-02
+last_modified: 2026-10-03
 ---
 
 Use this checklist when creating a new repository from scratch. Follow the steps
@@ -94,7 +94,9 @@ Template files can be fetched from:
       `https://git.eeqj.de/sneak/prompts/raw/branch/main/.gitea/workflows/check.yml`
 - [ ] Language-specific:
     - [ ] Go: `go mod init sneak.berlin/go/<name>`, `.golangci.yml` (fetch from
-          `https://git.eeqj.de/sneak/prompts/raw/branch/main/.golangci.yml`)
+          `https://git.eeqj.de/sneak/prompts/raw/branch/main/.golangci.yml` and,
+          in the same commit, set the lint phase digest to the one named in the
+          `.golangci.yml` paragraph of `REPO_POLICIES.md`)
     - [ ] JS: `yarn init`, `yarn add --dev prettier`
     - [ ] Python: `pyproject.toml`
 

prompts/REPO_POLICIES.md

@@ -454,13 +454,15 @@ style conventions are in separate documents:
   v2.14.0 (released 2026-09-24), pinned as the digest of the lint phase's base
   image
   (`golangci/golangci-lint@sha256:ad862ba6b3798cbe0fd9fd7408d498fd74fbd2623a92406b2fd3898faf0bf98f`,
-  which reports `2.14.0 built with go1.27.0 from 114493f9`). A golangci-lint
+  which reports `2.14.0 built with go1.27.0 from 114493f9`). A module's `go`
-  built with go1.26 refuses to lint a module whose `go` directive is 1.27 or
+  directive must not name a newer Go minor version than the one golangci-lint
-  later, so a new Go version needs a golangci-lint built with it. That digest is
+  was built with, or golangci-lint refuses to lint it: this release lints
-  the only pin, since no repo installs golangci-lint on the host. A repo moving
+  `go 1.27.1` but not `go 1.28`. That digest is the only pin, since no repo
-  to a new version changes that digest and re-vendors `.golangci.yml` in the
+  installs golangci-lint on the host. A repo sets the lint phase digest to the
-  same commit, because a new release can add linters that `default: all`
+  one named here and re-vendors `.golangci.yml` in the same commit, whichever of
-  switches on until the canonical copy disables them.
+  the two prompted the change: the canonical copy can name linters that an older
+  golangci-lint rejects, and a newer golangci-lint can add linters that
+  `default: all` switches on until the canonical copy disables them.
 
 - **`script/bootstrap` installs a pinned tool by comparing versions, never by
   testing presence.** An `if ! command -v <tool>; then install; fi` guard tests