Add test coverage for CGM device profiles #10

What

The CGM (Continuous Glucose Monitor) device profiles in packages/core/src/profiles/cgm.ts define DEXCOM_SHARE_CGM, LIBRE_LINKUP_CGM, and GENERIC_GLUCOSE_METER but have no dedicated test file.

Where

• Source: packages/core/src/profiles/cgm.ts
• New test: packages/core/src/__tests__/profiles-cgm.test.ts

How

1. Create a test file following the pattern in other test files
2. Test that each profile has the expected capabilities, service UUIDs, and brand/model values
3. Run pnpm test && pnpm lint

Acceptance Criteria

• Test file with 3+ tests (one per profile)
• All tests pass