fix(ship): accept case-insensitive --bump levels in gstack-next-version (#2770)

[loulanyue]

Summary of Changes

In /ship, Step 12 records bump levels in uppercase (e.g., MICRO, PATCH, MINOR, MAJOR) as defined in ship/SKILL.md. However, bin/gstack-next-version strictly validated against lowercase strings, exiting with code 2. Because stderr was silenced with 2>/dev/null || echo '{"offline":true}', this caused queue-aware shipping to falsely report that the queue was offline and fall back to local arithmetic on every ship.

Solution

1. Normalize to lowercase: In bin/gstack-next-version:parseArgs, normalize bump.toLowerCase() before validating against ["major", "minor", "patch", "micro"].
2. Export parseArgs: Exported parseArgs for unit testing.
3. Unit Tests: Added regression tests in test/gstack-next-version.test.ts verifying uppercase and mixed-case bump levels (MICRO, PATCH, Minor, MAJOR). All 57 tests pass.

Fixes #2770

[trunk-io]

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