v0.7.0a15

What's Changed

• chore(release): prepare 0.7.0a15 — changelog + deep-review fixes
• fix(realtime): prefer NumPy resampler to unblock SIP audio pacing
• style(delivery): apply ruff format to WaitForIdle warning log
• feat(realtime): voice observability + delivery robustness
• feat(sip): PSTN-compatibility improvements for outbound dial

Full Changelog: v0.7.0a14...v0.7.0a15