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 it will be assigned to you.

Please hold one open claim at a time. Once the pull request for it is merged,
say which issue you want next and it will be assigned. That keeps issues from
sitting claimed while another is still in review, so other newcomers can see
what is genuinely free.

[YANGCHUNHONG3000]

I'd like to work on this meter-value-zero scenario.

[sepehr-safari]

Thanks for the interest. I am assigning these one at a time, and #104 is with you
now, so I am leaving this one open for the moment. Once #133 merges, say the word
and it is yours.