fix(test): add TestMain to isolate cmd/opencodereview from the real home

[JasonBuildAI]

Description

Running the cmd/opencodereview test binary on Windows no longer writes review session files into the developer's real ~/.opencodereview/sessions/. A package-level TestMain redirects HOME and USERPROFILE to a temporary directory for every test in the package.

Value: anyone running go test ./cmd/opencodereview/ (or make test) on Windows keeps their real session history, and the ocr viewer session list, free of test-generated entries.

os.UserHomeDir() resolves USERPROFILE on Windows, not HOME, so the 13 t.Setenv("HOME", t.TempDir()) call sites in this package never redirected the home there. Follow-up to #1416, which added this guard to internal/session, internal/agent, internal/llmloop and internal/scan: cmd/opencodereview was the remaining package without it.

Fixes #1706

Type of Change

• Bug fix (non-breaking change that fixes an issue)

How Has This Been Tested?

Windows 11 (NT 10.0.26200.0), Go 1.26.9 windows/amd64, at commit 357c3f0. Method: snapshot the file list under %USERPROFILE%\.opencodereview, run the command, compare.

1. Unmodified main, targeted run:
   go test -count=1 -run 'TestRunSessionCompare|TestSessionCompareCompletesBothPositionals|TestScanBudgetJSON|TestValidateResumeIdentity' ./cmd/opencodereview/
   -> 23 files added under %USERPROFILE%\.opencodereview\sessions\, e.g.
   \sessions\D_Temp-TestRunSessionCompare_TextShowsCounts4049144688-002\153542f9-98b3-45b3-8ec2-841d065d66f1.jsonl
\sessions\D_Temp-TestScanBudgetJSONbudget_stop_sets_budget_exceeded724104049-003\40e1a7a3-1ee4-4aaf-ab8b-4d4aaa3e82ba.jsonl

2. With this change:

   • go test -count=1 ./cmd/opencodereview/ -> ok github.com/alibaba/open-code-review/cmd/opencodereview 145.738s, 0 files added, 0 removed
   • make test (full suite, -race) -> exit 0, all 24 packages ok, 0 files added, 0 removed
   • make check -> exit 0; make build -> exit 0
   • %USERPROFILE%\.opencodereview\config.json unchanged: sha256 156BEFAFC67A6C486910E9D6D42D72EEB4DF705B2A71CE2481B3675A3E7F5C0C before and after

• make test passes locally
• Manual testing (describe below)

Checklist

• My code follows the project's coding style (go fmt, go vet) - make check passed
• I have performed a self-review of my code
• I have added tests that prove my fix is effective or my feature works - not applicable: this PR is test-infrastructure; the before/after snapshots above are the proof
• New and existing unit tests pass locally with my changes
• I have updated the documentation accordingly (if applicable)
• I have signed the CLA
• I did not use AI/LLM to create this PR, or I disclosed the tool/model below and reviewed its output; I did not attribute commits to AI and will answer maintainer questions and review comments myself without AI/LLM.

AI/LLM disclosure: investigated and drafted with the OpenAI Codex desktop agent (Codex CLI 0.162.0-alpha.17.2, GPT-5-class model), used at my request under constraints I set. I reproduced the leak, ran every command quoted above, and reviewed the full diff and this description before requesting review.

Related Issues

Fixes #1706

[github-actions]

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