Epic #74.10: SRP refactor stream_wayland_portal pipeline script

[ppotepa]

Parent: #74

Objective

Split hotspot file into smaller modules/components with single-responsibility boundaries.

Target

• File: host/scripts/stream_wayland_portal_h264.py
• Stack: Python
• Current size: ~1058 LOC

Scope

• Extract cohesive domains/functions into dedicated files/modules.
• Keep public behavior and contracts stable.
• Reduce file responsibility breadth and coupling.

Definition of Done

• Main hotspot file reduced and responsibilities separated.
• Existing checks/tests/smoke flows remain green.
• No functional regression in runtime behavior.