Prefer testutil.InitRepo in trivial git test setup

[pfleidi]

Summary

• clarify repo guidance to prefer testutil.InitRepo() over direct git.PlainInit() in trivial test setup
• convert verified-trivial normal-repo tests in explain_test.go, git_operations_test.go, phase_wiring_test.go, and session/state_test.go
• leave merge-heavy, no-config, and other non-trivial git.PlainInit() cases unchanged

Test Plan

• go test ./cmd/entire/cli ./cmd/entire/cli/session
• go build ./...
• go vet ./...

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Note

Low Risk
Test-only refactor and documentation update; behavior changes are limited to how temporary repos are configured (user identity/GPG signing), which may only affect tests that implicitly relied on missing config.

Overview
Standardizes unit-test git repository setup by replacing many direct git.PlainInit() calls with testutil.InitRepo(t, dir) (and git.PlainOpen when a *git.Repository is still needed), reducing dependence on global git config and avoiding GPG/user config pitfalls in CI.

Adds explicit documentation in CLAUDE.md directing contributors to prefer testutil.InitRepo() for test repos, and introduces a small helper (initOpenedTestRepo) to de-duplicate this pattern in git_operations_test.go.

^{Reviewed by Cursor Bugbot for commit 58ce965. Configure here.}

[Copilot]

Pull request overview

This PR standardizes trivial git test setup across the CLI by preferring testutil.InitRepo(t, dir) over direct git.PlainInit() calls, aligning tests with the repo’s documented guidance for consistent repo-local config in CI.

Changes:

• Replaced trivial git.PlainInit() usage with testutil.InitRepo() in several test files.
• Added a small helper in git_operations_test.go to reduce repetition when initializing and opening a repo.
• Updated CLAUDE.md to explicitly document the preference for testutil.InitRepo() in tests.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
cmd/entire/cli/session/state_test.go	Uses testutil.InitRepo() for temp repo setup in git-common-dir cache tests.
cmd/entire/cli/phase_wiring_test.go	Switches phase wiring test repo setup to testutil.InitRepo().
cmd/entire/cli/git_operations_test.go	Introduces initOpenedTestRepo helper and replaces direct PlainInit in several tests.
cmd/entire/cli/explain_test.go	Converts multiple tests to initialize repos via testutil.InitRepo() (opening the repo where needed).
CLAUDE.md	Documents the repo convention to prefer testutil.InitRepo() over git.PlainInit() in tests.

[alishakawaguchi]

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