Add Together AI secret detector

[asivaprasad09]

Summary

• Adds a new detector for Together AI API keys (tgp_v1_ format)
• Verifies keys via read-only GET https://api.together.xyz/v1/models
• Registers detector in defaults.go and proto as TogetherAI = 1049
• Populates SecretParts with "key" per detector conventions

Test plan

• go test ./pkg/detectors/togetherai/... -tags=detectors passes all 4 cases (found+verified, found+unverified, not found, timeout)
• Verified against a real Together AI key returning HTTP 200
• Invalid key correctly returns HTTP 401 (unverified, no error)

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Note

Low Risk
Low risk: additive new detector plus enum registration; main risk is potential false positives/verification HTTP behavior from the external Together API.

Overview
Adds a new TogetherAI secret detector that finds tgp_v1_... API keys and can verify them via a read-only GET https://api.together.xyz/v1/models call.

Registers the detector in defaults.go and extends detector_type.proto/generated protobufs with TogetherAI = 1049, with tests/benchmarks covering verified, unverified, not-found, and timeout verification cases.

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❌ Akshara Sivaprasad
❌ cursoragent

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