fix(test): isolate runtime worktree env fixtures

[bouillipx]

What

• Isolate install/runtime worktree test subprocess environments from ambient runtime session variables.
• Add shared sanitizers for runtime worktree fixture tests so active session values do not change fixture branch/dir expectations.
• Scope is test harness only: two files under packages/api/test.

Why

The scheduler missed-ledger branch was blocked by unrelated baseline gate failures. The failing install/runtime worktree suites inherited active session variables such as CAT_CAFE_RUNTIME_BRANCH and CAT_CAFE_RUNTIME_DIR, while their fixtures expected runtime/main-sync. That made main red under this local runtime session and hid the scheduler signal.

Issue Closure

• None. Patrol baseline gate cleanup discovered during scheduler review.

Original Requirements

• Source: scheduled patrol mission, 2026-07-12 00:00 Asia/Shanghai.
• Excerpt: inspect Clowder Code / Cat Cafe for imperfect, improvable, competitiveness-relevant areas; verify truth sources and evidence first; close executable findings through lifecycle, implementation, gate, review, and completion records.
• Operator pain: scheduler work should not be blocked by unrelated environment-sensitive baseline tests.
• Reviewer check: this PR should only remove ambient env pollution from test fixtures, not change runtime behavior.

Plan / ADR

• Plan: patrol finding from scheduler baseline gate attribution.
• ADR: none.
• BACKLOG: none.

Tips Contribution

• Added or updated tips
• Existing tip sourceRef still covers this user-visible change
• tips_exempt: internal test harness stabilization; no user-visible capability change.

Tradeoff

This does not change runtime-worktree.sh behavior. It confines the fix to test subprocess env setup so production/runtime semantics remain untouched.

Test Evidence

• Targeted RED before fix: install/runtime worktree suites had 40 pass / 5 fail under inherited runtime env.
• Targeted GREEN after fix: with Node 24 and shared-state preflight disabled, install/runtime worktree suites pass 45/45.
• pnpm check: pass.
• pnpm gate: pass on fix/runtime-worktree-baseline-gate at f5d7997, rebased onto origin/main.
• git diff --check origin/main...HEAD: clean.
• Root artifact guard: no root media/design artifacts.

Open Questions

• Please verify the env sanitizer is narrow enough: clears runtime fixture pollution without hiding variables each test intentionally sets.

---

Local Review: [x] Maine Coon GPT-5.4 reviewed f5d7997 and gave scoped APPROVE.
Cloud Review: [ ] PR comment trigger pending after creation.

[bouillipx]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. 👍

Reviewed commit: f5d799702d

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