fix(vscode): prevent Windows gh console flashes

[marius-kilocode]

Fixes #12912

On Windows with Windows Terminal configured as the default terminal, Agent Manager background gh calls can cause older GitHub CLI releases to launch tzutil.exe as a visible child during local timezone lookup. Because gh is started hidden, the descendant is not hidden and can briefly steal focus.

This adds a single execGhRead boundary for Agent Manager read-only gh commands. On Windows, it preserves an existing TZ value and otherwise supplies TZ=UTC, preventing the CLI from falling back to tzutil.exe without changing write-capable command paths. PR status polling and PR import now use the boundary, and an architecture test prevents future Agent Manager gh literals from bypassing it.

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Files Reviewed (7 files)

• .changeset/fix-gh-windows-console.md
• packages/kilo-vscode/AGENTS.md
• packages/kilo-vscode/src/agent-manager/PRStatusPoller.ts
• packages/kilo-vscode/src/agent-manager/WorktreeManager.ts
• packages/kilo-vscode/src/agent-manager/gh.ts
• packages/kilo-vscode/tests/unit/agent-manager-arch.test.ts
• packages/kilo-vscode/tests/unit/gh.test.ts

lgtm — the execGhRead boundary is well-scoped: it only injects TZ=UTC on win32 when no case-variant of TZ is set, delegates to the existing windowsHide-enforcing wrapper, and all former gh call sites (probe, PR view/list/checks, repo view, GraphQL comments, PR import) are routed through it with their original options intact. The arch test guards against future bypasses, and gh.test.ts exercises the real code path with a real child process instead of mocks. No new long-lived resources, so no leak potential.

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_{Reviewed by kimi-k3 · Input: 61.4K · Output: 12.3K · Cached: 630.8K}

_{Review guidance: REVIEW.md from base branch main}