Add a new scenario: meter-value-zero

[sepehr-safari]

Good First Issue

Add a new scenario meter-value-zero — a session where meter values are always zero (potential meter malfunction).

What to do

1. Create packages/toolkit/src/scenarios/__scenarios__/meter-value-zero.ts
2. Create a synthetic trace with meter values all reporting "0" during an active transaction
3. Set expectedFailures: ['METER_VALUE_ANOMALY'] (zero is not negative, but is anomalous)
4. Import and register in packages/toolkit/src/scenarios/index.ts
5. Update scenario count in tests
6. Run ocpp-debugkit ci to verify

Files to modify

• packages/toolkit/src/scenarios/__scenarios__/meter-value-zero.ts (new)
• packages/toolkit/src/scenarios/index.ts (register)
• packages/toolkit/src/scenarios/index.test.ts (update count)
• tests/external-fixture/test.mjs (update count)

How to claim

Comment "I'd like to work on this" and we'll assign it to you.