#16617: fix(voice-call): preserve Telnyx inbound event direction metadata

## Describe your changes - Preserve Telnyx `call.initiated` metadata (`direction`, `from`, `to`) during webhook normalization instead of dropping those fields. - Normalize provider direction aliases in a shared helper and reuse it across Telnyx, Twilio, and Plivo providers for consistent event semantics. - Add endpoint-based fallback direction inference in call event processing so inbound calls are still identified when providers omit an explicit direction value. ## Screenshot or video (only for visual changes) - N/A ## GitHub Issue Link (if applicable) - https://github.com/openclaw/openclaw/issues/16601 ## Testing Plan - Explanation of why no additional tests are needed: - Added focused unit coverage for Telnyx webhook parsing and inbound direction inference paths in the call manager. - Unit Tests (JS and/or Python): - `pnpm test -- extensions/voice-call/src/providers/telnyx.test.ts extensions/voice-call/src/manager/events.test.ts extensions/voice-call/src/providers/twilio.test.ts extensions/voice-call/src/providers/plivo.test.ts` - E2E Tests: - Not run (provider integrations require external telephony services). - Any manual testing needed?: - Optional: place an inbound Telnyx call and confirm `call.initiated` creates an inbound call record. --- **Contribution License Agreement** By submitting this pull request you agree that all contributions to this project are made under the Apache 2.0 license.