ci: gate gofmt in golangci-lint, add make fmt

[shadowbrush]

Follow-up to #329, which fixed six drifted files. This stops the drift recurring silently.

Nothing enforced formatting before: .golangci.yml had no formatters section and no workflow shelled out to gofmt, so the drift was invisible to CI.

The change

formatters:
  enable:
    - gofmt
  exclusions:
    generated: strict

Enabling the gofmt formatter makes golangci-lint run report a formatting diff as an issue and exit non-zero. That gates both make lint locally and the CI lint job — golangci-lint-action runs run by default — so no workflow change is needed.

Plus a make fmt target (golangci-lint fmt) so a failing gate has an obvious remedy, and a line in CLAUDE.md's command list.

Generated code is excluded, and I verified it

genqlient's output would otherwise be a trap: you can't hand-fix it, since make generate rewrites the file. exclusions.generated: strict keys off the standard header, which internal/api/gen/generated.go carries:

// Code generated by github.com/Khan/genqlient, DO NOT EDIT.

Injecting drift into that file:

$ gofmt -l internal/api/gen/
internal/api/gen/generated.go      # gofmt sees it
$ golangci-lint run
0 issues.                          # linter correctly ignores it

Verified end to end

clean tree            → make lint  0 issues, exit 0
inject drift          → make lint  "File is not properly formatted (gofmt)", exit non-zero
make fmt              → repairs it byte-for-byte
                      → make lint  exit 0, tree back to clean

The failure output names the file, line, and offending source line:

internal/cmdutil/memref_test.go:7:1: File is not properly formatted (gofmt)
		"acme.com:kb":   "hrn:mem:acme.com:kb",  // single colon → canonical v2
^

go test ./... — 16 packages green. make lint — 0 issues.

One thing to expect

Any in-flight branch that has drifted will start failing the lint job until it runs make fmt. main is clean as of #329, so nothing is failing now.

🤖 Generated with Claude Code

[gemini-code-assist]

Caution

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[shadowbrush]

@codex review

[Copilot]

Pull request overview

This PR tightens the Go formatting contract by making gofmt enforcement part of the existing golangci-lint gate, preventing formatting drift from silently accumulating in the repo’s Go codebase.

Changes:

• Enable the gofmt formatter in .golangci.yml so golangci-lint run fails on formatting diffs.
• Add make fmt as the standard remediation path via golangci-lint fmt.
• Document the new formatting gate and make fmt in CLAUDE.md.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
Makefile	Adds a fmt target (golangci-lint fmt) and marks it phony to provide an easy fix path for formatting-gate failures.
CLAUDE.md	Updates the developer command list to reflect that make lint gates gofmt and introduces make fmt.
.golangci.yml	Enables the gofmt formatter and excludes generated code (generated: strict) to avoid non-actionable failures on committed generated output.

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[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. What shall we delve into next?

Reviewed commit: 93681569ab

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