chore(video): remove deprecated Sora provider

[lelandg]

Sora (OpenAI) is deprecated and should be removed from the codebase. It is still wired across ~6 files:

• core/video/sora_client.py — the client (~1400 lines)
• core/video/__init__.py — lazy SoraClient/SoraModel/SoraGenerationConfig/SoraGenerationResult/SoraErrorType exports + SORA_AVAILABLE
• core/video/config.py — default_video_provider comment lists "sora" as an option
• gui/video/video_project_tab.py — 'OpenAI Sora' routing + the full _generate_video_clip_sora() path (+ sora_model/sora_resolution kwargs)
• gui/video/workspace_widget.py — Sora references in the provider flow
• tests/video/test_video_provider_persistence.py — Sora cases

Scope

• Remove the Sora client, exports, GUI provider option + generation path, config references, and Sora-specific tests.
• Verify the remaining providers (Slideshow, Veo, Gemini Omni) still select/persist correctly and the video tests stay green.
• Confirm no dangling SORA_* / 'OpenAI Sora' references remain.

Notes

• Surfaced while scoping CLI video support (Omni + Veo only). Keep this as its own focused PR, separate from the CLI-video feature.
• Found by Claude (Claude Code) on 2026-06-30.

[skip-agent]

[lelandg]

Removed the deprecated Sora provider (merged to main locally as 6a5219c).

What changed

• Deleted core/video/sora_client.py; removed the lazy Sora* exports + SORA_AVAILABLE from core/video/__init__.py.
• Removed the Sora provider combo item, sora_model_combo/sora_resolution_combo, handlers, visibility toggles, and save/restore from gui/video/workspace_widget.py.
• Removed the 'OpenAI Sora' routing + _generate_video_clip_sora() + sora kwargs + SoraClient import from gui/video/video_project_tab.py.
• Dropped Sora from core/video/config.py (default_video_provider now slideshow/veo/omni) and from the persistence tests.
• Stripped the Sora section/bullet/tooltip from README.md (left the dated Plans/*.md and Discord announcement as historical records).

Back-compat (decided: coerce to Omni + notify)

• Config migration coerces default_video_provider "sora" → "omni" (idempotent, logged).
• Loading a project saved with "OpenAI Sora" coerces it to Gemini Omni, logs a warning, and shows a "Provider Removed" dialog prompting a re-save.

Also fixed an UnboundLocalError on the new coercion path (function-local import logging shadowed the module import).

Verification: grep for live Sora symbols returns zero; full suite 440 passing (tests/video + tests/layout); a most-capable-model review passed (no Critical/Important). GUI paths can't be exercised headlessly (AGENTS.md §6) — leaving this open pending a PowerShell GUI smoke check on the Video tab (provider list shows Slideshow/Veo/Omni only; loading an old Sora project shows the coercion dialog and switches to Omni).

— Fixed by Claude (Claude Code)

[lelandg]

GUI smoke check passed (verified by Leland): Video tab provider list shows Slideshow / Gemini Veo / Gemini Omni only, and loading a project saved with OpenAI Sora coerces to Gemini Omni with the "Provider Removed" notification.

Merged and pushed to main (6a5219c). Closing.

— Claude (Claude Code)