Resolve cron optional peer CI timeout

[ayden94]

Summary

Stabilize the cron optional Redis peer root-barrel import contract test that timed out twice in CI while blocking PR #2314.

Linked context: follow-up for PR #2314 CI blocker.

Changes

• Give the root-barrel optional peer dynamic import test an explicit timeout budget.
• Keep the existing assertions and optional Redis peer contract unchanged.

Testing

• pnpm exec biome check packages/cron/src/optional-redis-peer.test.ts
• pnpm --filter @fluojs/cron... build
• pnpm --filter @fluojs/cron typecheck
• pnpm --filter @fluojs/cron test -- src/optional-redis-peer.test.ts

Release impact

• This PR has consumer-visible release impact and includes a changeset.
• This PR has no consumer-visible release impact.

Test-only CI stabilization; no .changeset/*.md file is required.

Public export documentation

No public exports changed.

• Changed public exports include a source-level summary.
• Changed exported functions document matching @param / @returns tags where applicable.
• Source @example blocks and README scenario examples still play complementary roles.

Behavioral contract

This PR preserves the existing optional Redis peer root-import contract and only adjusts the test timeout budget.

• No documented behavioral contracts were removed without migration notes.
• New behavioral contracts are documented in the affected package README.
• Intentional limitations are explicitly stated (not silently removed).
• Runtime invariants are covered by regression tests.

Platform consistency governance (SSOT)

No platform contract or governance docs changed.

• SSOT English/Korean mirror structure remains synchronized for changed governance docs.
• If platform contract docs changed, companion updates include discoverability/docs index, tooling or CI enforcement, and regression-test evidence.
• Any package README alignment/conformance claims are backed by createPlatformConformanceHarness(...) tests.