test(memdir): serialize hosted-memory path tests against the home env lock

[BunsDev]

Summary

Fixes the intermittent CI failure in memdir::tests::hosted_memory_ignores_local_checkout_path (Actions run 30271680167; Cave bead cave-r78ad): the test — plus two sibling hosted-path tests — resolved home-dependent memory paths without holding COVEN_HOME_ENV_LOCK, so a parallel test's COVEN_CODE_TEST_HOME set_var/remove_var could flip the home between two resolutions and break equal-path assertions.

The audit found every mutator already holds the lock (including claudemd's), and CONFIG_HOME_ENV_LOCK is a re-export of the same mutex — one lock covers all; these three were the only unlocked readers. Each now takes the shared lock and pins a private tempdir home for its duration (restored after), matching the module's mutating-test convention, so the assertions are hermetic as well as serialized.

Verification

• memdir:: module: 41/41 across repeated runs.
• cargo fmt --check clean.

🤖 Generated with Claude Code

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Project	Deployment	Actions	Updated (UTC)
docs	Ready	Preview	Jul 31, 2026 4:32pm

[Copilot]

Pull request overview

This PR addresses intermittent CI flakiness in memdir hosted-memory path tests by serializing home-directory resolution against other tests that mutate COVEN_CODE_TEST_HOME, ensuring path resolution and assertions run against a stable, test-private home.

Changes:

• Added COVEN_HOME_ENV_LOCK acquisition around hosted-memory path resolution in three tests.
• Pinned COVEN_CODE_TEST_HOME to a private tempdir for the duration of each affected test (restoring afterward).
• Documented the race scenario and why serialization is required.

Suppressed comments (2)

src-rust/crates/core/src/memdir.rs:1142

• COVEN_CODE_TEST_HOME is restored after the assertions. If an assertion panics, the env var stays set and can affect other tests that run after this one. Restore the env var before assertions (or use a Drop guard) so failures don’t leak process-global state.

        match original_test_home {
            Some(value) => std::env::set_var("COVEN_CODE_TEST_HOME", value),
            None => std::env::remove_var("COVEN_CODE_TEST_HOME"),
        }

src-rust/crates/core/src/memdir.rs:1244

• COVEN_CODE_TEST_HOME is restored only after assertions. If an assertion panics, the env var stays set and can leak into other tests. Restore the env var before running assertions so failures don’t contaminate subsequent tests.

        match original_test_home {
            Some(value) => std::env::set_var("COVEN_CODE_TEST_HOME", value),
            None => std::env::remove_var("COVEN_CODE_TEST_HOME"),
        }

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