test: free RAM between multi-package describes to fix CI OOM

[ryukzak]

Why

The Canary & Release job has been OOM-killed (make: *** [Makefile:34: test] Killed, exit 143) on ubuntu-latest during test/api/write-generator/multi-package/sql-on-fhir.test.ts. The kernel SIGKILLs bun test once resident memory exceeds the runner's ~7 GiB. Re-runs are deterministic-fail.

Root cause

All three multi-package test files use top-level await inside describe:

describe("TypeScript Generation", async () => {
    const result = await new APIBuilder(...).generate();
    it("...", () => { expect(result...)... });
});

Two compounding problems:

• Top-level awaits inside describe resolve during discovery, so every section's result is built upfront — three (or four) results live concurrently per file.
• result is captured by every it() in the section, so GC can't reclaim it for the file's lifetime.

Each result.filesGenerated is a Record<string, string> of full file contents (CDA TS: 124 files, SQL-on-FHIR + R5 deps: 45+ R5 files plus generators × 3). With bunfig.toml setting parallel = true, multiple files' worth of residency pile up at the same time.

Fix

Move generation into beforeAll and null the result in afterAll (+ Bun.gc(true)) so each section's payload can be reclaimed before the next section starts:

describe("TypeScript Generation", () => {
    let result: GenerationReport;
    beforeAll(async () => { result = await new APIBuilder(...).generate(); });
    afterAll(() => { result = undefined as unknown as GenerationReport; Bun.gc(true); });
    it("...", () => { expect(result...)... });
});

Applied to:

• test/api/write-generator/multi-package/cda.test.ts
• test/api/write-generator/multi-package/local-package.test.ts
• test/api/write-generator/multi-package/sql-on-fhir.test.ts

Verification

• bun run typecheck — clean
• bun run lint — only pre-existing warnings in src/typeschema/utils.ts
• bun test — 257 pass, 0 fail, 75 snapshots intact
• Local peak RSS (macOS) dropped to ~6.08 GiB; the OOM only reproduces on ubuntu-latest, so CI on this PR is the real check.