feat(simulate): sip_inbound_trunk_id transport field for carrier pinning

[azain-commits]

Summary

Adds TelephonyTransport.sip_inbound_trunk_id so a sip_inbound run can pin the leased carrier pool trunk (e.g. a Telnyx pool) instead of inheriting the worker's default LIVEKIT_INBOUND_TRUNK_ID. The SDK stays carrier-blind — it receives trunk ids / E.164 / dispatch-rule names, never "twilio"/"telnyx" logic. Backward compatible: the field is optional and defaults to None, so existing runs are unchanged. Part of a 3-repo Telnyx effort (companion PRs in future-agi and livekit-infra).

What changed

• agent/definition.py — new optional sip_inbound_trunk_id field on TelephonyTransport; validator forbids it on sip_outbound and web transports (webrtc/vapi_websocket/retell_webcall).
• simulation/engines/livekit.py — _ensure_sip_inbound_dispatch now:
  • prefers transport.sip_inbound_trunk_id over the LIVEKIT_INBOUND_TRUNK_ID env;
  • when reusing a named dispatch rule, validates the rule's trunk_ids contain the pinned trunk (raises sip_inbound_rule_trunk_mismatch otherwise) — so a stale/other-carrier rule of the same name can't route onto the wrong trunk;
  • falls back to the env only when neither a dispatch rule nor an explicit trunk id is set (self-provision path).
• endpoints/profiles.py — LIVEKIT_INBOUND_TRUNK_ID is required only when neither a dispatch rule nor an explicit inbound trunk id is present.

Why

The hosted runner leases a carrier-specific inbound pool trunk per run; without a way to pin it, a sip_inbound run falls back to the worker's ambient inbound trunk (one carrier). A neutral transport field keeps the SDK provider-agnostic while letting the platform select the trunk per run and supporting concurrent carriers.

Tests

• SDK compiles; TelephonyTransport validation covered by the model validator.
• tests/runtime/test_livekit_engine.py + tests/test_voice_simulation.py: no new failures — the 5 failing engine tests (test_managed_case_dispatches_..., test_sip_outbound_dials_..., 3× test_web_bridge_joins_...) are pre-existing (incomplete mocks / SIP infra), confirmed identical on the branch tip with these changes stashed.

Pre-existing issues (not introduced here)

• The 5 test_livekit_engine.py failures above pre-date this PR (verified via stash-baseline).

Backward compatibility

• sip_inbound_trunk_id is optional (None default). With no dispatch rule and no trunk id, behaviour is exactly as before (env-driven self-provision).

[azain-commits]

Telnyx provider — 3-repo PR set:

• livekit-infra (carrier port + provisioning): https://github.com/future-agi/livekit-infra/pull/36
• future-agi (backend carrier selection): feat(simulate): Telnyx telephony provider — hosted SIP carrier selection future-agi#2162
• agent-learning-kit (SDK sip_inbound_trunk_id): feat(simulate): sip_inbound_trunk_id transport field for carrier pinning #59

Suggested review/merge order: livekit-infra → agent-learning-kit → future-agi.