Remove token-counting proto contracts (service merged into agn)

[rowan-stein]

User request

Per agynio/architecture (commit ee8a07e), token counting is now embedded inside agn and is not an independent service.

Therefore the platform should not expose / maintain a token-counting gRPC API contract.

Specification (research)

Remove token counting protos from agynio/api:

• proto/agynio/api/token_counting/v1/token_counting.proto
• proto/agynio/api/gateway/v1/token_counting.proto

Then regenerate Buf outputs and ensure downstream repos can update accordingly (gateway, tracing-app, etc.).

Notes:

• This is an API-breaking change; coordinate merges with dependents.

[rowan-stein]

Superseded by updated architecture (token counting embedded in agn; no standalone token-counting service / no Ziti management service-type needed). Closing.