Lint's .golangci.yml check says which fix applies (closes #34)

backend/script/lint compared .golangci.yml with its pinned sha256 and,
on any failure, said to restore the file from sneak/prompts. Once the
org standard has legitimately changed, that advice loops: the copied
file is right and GOLANGCI_CONFIG_SHA256 is stale. On a mismatch the
script now says to compare the file with the org standard, restore it
if they differ, and update GOLANGCI_CONFIG_SHA256 if they are the same;
it still prints both hashes. A missing .golangci.yml, and a sha256sum
that is missing or prints no hash, get their own messages instead of
being reported as a mismatch. Each failure still exits 1. .golangci.yml
is unchanged.

Model: opus-5-5

TODO.md

@@ -23,6 +23,14 @@ latest run passes.
 
 # Completed Steps
 
+- 2026-10-03: `backend/script/lint` says what went wrong with its
+  `.golangci.yml` check (issue #34). On a hash mismatch it says to compare the
+  file with the org standard: if they differ, restore the org standard; if they
+  are the same, the org standard changed, so update `GOLANGCI_CONFIG_SHA256` in
+  that script. It used to say only to restore the file, which loops once the org
+  standard itself has moved. A missing `.golangci.yml`, and a `sha256sum` that
+  is missing or prints no hash, each get their own message instead of being
+  reported as a mismatch; every one still fails the lint
 - 2026-10-03: the Go tests run with the race detector and coverage (issue #88):
   `backend/script/test` runs `go test -timeout 30s -race -cover ./...` and, if
   that fails, runs it again with `-v` and fails. Go's `-timeout` bounds the