Bump moonbitlang/async to 0.22.4

[bobzhang]

Bump moonbitlang/async to 0.22.4 (latest).

Since async 0.22.0, catch no longer captures cancellation; cleanup must live in defer/errdefer. This PR bumps the dependency and audits every catch around async code.

Change: Bump moonbitlang/async 0.20.3 → 0.22.4. No source changes.

Cancellation audit: 3 catch sites in main.mbt reviewed (stderr write, error → message/exit/abort); try! blocks let cancellation pass through. None changed.

Verification: root 73 (wasm-gc, js) / 74 (native, wasm), tests 18 on all targets, debug and --release, identical before and after; the CLI regenerates tests/calc_test/calc.mbt byte-for-byte on native and wasm.

Commits:

• d588ef8 chore(deps): bump moonbitlang/async to 0.22.4

🤖 Generated with Claude Code

[bobzhang]

Automated review by Codex CLI:

No actionable findings. Reviewed the requested diff and commit log.

• Only change: async 0.20.3 → 0.22.4.
• No cleanup migrations needed: async catch handlers only suppress/report errors; no missed cleanup sites found.
• Dependency file helpers use defer file.close(), closing once on success, error, or cancellation.
• No affected cancellation APIs, task-group callbacks, formatting, or .mbti changes.
• No additional application behavior changes identified.

Static review only; builds/tests were not run under the read-only constraint.

VERDICT: APPROVE

CI green. Merging as a low-risk dependency bump; a release follows.

🤖 Generated with Claude Code