Fix git ownership and -race in the canonical Go Dockerfile (closes #73)

The test phase ran go test -race on the alpine Go image, which has no C
compiler, so cgo was off and the phase failed with "-race requires cgo"
before running a test. It now uses the Debian Go image.

A build context sent as a tar stream keeps the sender's file owners, so
git in the stage that compiles refused the checkout and the version came
out empty. That stage now runs
git config --system --add safe.directory /src, and the policy text and
both checklists say why. The apk add --no-cache git line is unchanged:
its pinning waits on #72.

Model: opus-5-5

.golangci.yml

@@ -17,7 +17,6 @@ linters:
   disable:
     # Genuinely incompatible with project patterns
     - exhaustruct      # Requires all struct fields
-    - exhaustruct_v5   # Requires all struct fields (successor to exhaustruct)
     - godot            # Requires comments to end with periods
     - wrapcheck        # Too verbose for internal packages
     - varnamelen       # Short names like db, id are idiomatic Go

TODO.md

@@ -28,13 +28,6 @@ fmt-check, and commit.
   because a context sent as a tar stream keeps the sender's file owners and git
   refuses that checkout, leaving the version empty. Both checklists state that
   step in the same words.
-- 2026-10-03: Moved the canonical golangci-lint to v2.14.0, built with go1.27,
-  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`. 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

@@ -84,9 +84,7 @@ 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` and,
-          in the same commit, set the lint phase digest to the one named in the
-          `.golangci.yml` paragraph of `REPO_POLICIES.md`)
+          `https://git.eeqj.de/sneak/prompts/raw/branch/main/.golangci.yml`)
     - [ ] 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

@@ -98,9 +98,7 @@ 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` and,
-          in the same commit, set the lint phase digest to the one named in the
-          `.golangci.yml` paragraph of `REPO_POLICIES.md`)
+          `https://git.eeqj.de/sneak/prompts/raw/branch/main/.golangci.yml`)
     - [ ] JS: `yarn init`, `yarn add --dev prettier`
     - [ ] Python: `pyproject.toml`
 

prompts/REPO_POLICIES.md

@@ -457,18 +457,12 @@ style conventions are in separate documents:
   `test-support` depguard rule, where a repo names its own test-support packages
   by full import path. A repo adds entries there and changes nothing else, and a
   re-vendor carries its entries forward. The canonical golangci-lint version is
-  v2.14.0 (released 2026-09-24), pinned as the digest of the lint phase's base
+  v2.12.2 (released 2026-05-06), 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 module's `go`
-  directive must not name a newer Go minor version than the one golangci-lint
-  was built with, or golangci-lint refuses to lint it: this release lints
-  `go 1.27.1` but not `go 1.28`. That digest is the only pin, since no repo
-  installs golangci-lint on the host. A repo sets the lint phase digest to the
-  one named here and re-vendors `.golangci.yml` in the same commit, whichever of
-  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.
+  (`golangci/golangci-lint@sha256:5cceeef04e53efe1470638d4b4b4f5ceefd574955ab3941b2d9a68a8c9ad5240`,
+  which reports `2.12.2 built with go1.26.2 from c0d3ddc9`). That digest is the
+  only pin, since no repo installs golangci-lint on the host: bumping the
+  version means changing it and nothing else.
 
 - **`script/bootstrap` installs a pinned tool by comparing versions, never by
   testing presence.** An `if ! command -v <tool>; then install; fi` guard tests