AetherEngine 5.18.0

Fixed

IPT-only Dolby Vision (HEVC P5, AV1 P10.0) fails the load with a clear error when it would start on the software path, instead of playing with a green/purple color cast (#176 follow-up).

5.17.5 fixed the probe misroute that sent HEVC P5 to the software path. This release closes the same class of defect structurally:

• AV1 DV Profile 10.0 (compat 0) carries the same IPT-PQ-c2-only signal as HEVC P5 and no HDR10/HLG/SDR-compatible base layer. On devices without hardware AV1 decode (all Apple TVs, M1/M2 Macs, pre-A17 iPhones) it routes to dav1d, where the IPT signal renders with the same green/purple cast. Unlike HEVC P5 there is no native fallback to prefer: AVPlayer's HLS pipeline requires hardware AV1. No route on such devices can render P10.0 color-correctly, so the load now fails fast with AetherEngineError.dolbyVisionUnplayableOnSoftwarePath and a clear player-state message.
• HEVC P5 had two remaining doors into the software path after 5.17.5 (forward-only sources, which the native path cannot serve, and the test override). Both now fail fast the same way.

P7 / P8.x and AV1 P10.1 / P10.2 / P10.4 stay software-eligible: their base layer is self-contained HDR10 / SDR / HLG and decodes with correct color.

Added

• New public error case AetherEngineError.dolbyVisionUnplayableOnSoftwarePath(profile:) (hence the minor bump).

Covered by VideoRoutingPolicyTests (23 tests). Part of the #176 cleanup, reported by @ijuniorfu, triaged by @DrHurt.