test(cli): stabilize cross-platform env and path assertions

[tonyblu331]

🔗 Linked Issue

Closes #103

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🏷️ PR Type

• type:chore — Build, CI, or tooling changes

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📝 Summary

Stabilizes internal/cli tests on Windows: isolate HOME / USERPROFILE / APPDATA for agent discovery, set USERPROFILE in restore tests, use cmd.exe for quiet failure output on Windows, normalize path assertions with filepath.ToSlash, and use a temp GOBIN on PATH for the post-install note test.

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📂 Changes

File / Area	What Changed
internal/cli/cli_home_env_test.go	Shared helpers isolateAgentDiscoveryEnv, ensureOpenCodeSDDNodeStub
internal/cli/sync_test.go, restore_test.go, …	Call sites and SDD node stub for OpenCode
internal/cli/command_output_test.go	Windows vs Unix command for failure capture
internal/cli/run_path_guidance_test.go, run_notes_test.go	Path / env fixes

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🧪 Test Plan

go test ./internal/cli/... -count=1

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🤖 Automated Checks

Review budget: 172 / 400 (additions + deletions).

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✅ Contributor Checklist

• PR is linked to an issue with status:approved
• PR stays within 400 changed lines, or I have requested/obtained maintainer-applied size:exception with rationale documented
• I have added the appropriate type:* label to this PR
• Unit tests pass (go test ./...)
• E2E tests pass (cd e2e && ./docker-test.sh)
• I have updated documentation if necessary
• My commits follow Conventional Commits format
• My commits do not include Co-Authored-By trailers

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Chain Context

Field	Value
Chain	Standalone (Windows CLI test hardening)
Tracker PR	Not applicable
Position	1 / 1
Base	main
Depends on	None
Follow-up	None
Review budget	172 / 400
Starts at	main
Ends with	Green go test ./internal/cli/... on Windows

Chain Overview

main
 └── 📍 This PR (standalone)

Scope

• Includes: CLI test harness only
• Excludes: Engram feature code (see feat/engram-dd-* branches)

Autonomy

• CI is expected to pass for this PR branch
• This PR has one deliverable scope
• This PR can be rolled back without unrelated changes
• Tests cover this unit

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💬 Notes for Reviewers

Can land independently of the Engram data-directory stack. Supersedes overlapping test changes that were briefly on feat/engram-data-dir-wiring-v2.

[tonyblu331]

Closing this stale draft to clean up the Engram data-dir PR surface. The corrected work is being kept as a properly chained fork stack where each PR targets the previous branch and stays under the 400-line review budget.