feat(videogen): canonical video-generation surface + llama-swap client

New videogen/ contract package (ADR-0019): Request/Result/Model/Provider
with the imagegen conventions. Text-to-video and image-to-video are one
surface (Request.InitImage, nil = t2v) since hybrid checkpoints like
Wan 2.2 TI2V serve both from one model; Result carries a single clip.

provider/llamaswap gains VideoModel(id) targeting the blocking
POST {base}/v1/videos/sync (multipart, model-routed by the fork's new
video routes): vLLM-Omni parameter names, OpenAI-style input_reference
file part, optional fields stay off the wire so per-model launch-flag
defaults apply. CLAUDE.md package map picks up audio/ (missed in #12)
and videogen/.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AXQxVhXBw8PwFAtsVrXSmj

CLAUDE.md

@@ -34,6 +34,11 @@ majordomo        Registry, Parse, env-DSN loading, chain executor, re-exports
                  Tool/Toolbox, Capabilities, Stream, Model, Provider, errors
   imagegen/      canonical text-to-image contract: Request/Result/Model/
                  Provider (separate from llm; Image = llm.ImagePart)  (ADR-0016)
+  audio/         canonical speech contracts: SpeechModel (TTS) +
+                 TranscriptionModel (STT), same conventions      (ADR-0017)
+  videogen/      canonical video-generation contract: one Model for
+                 text-to-video + image-to-video (InitImage), single-clip
+                 Result (Image = llm.ImagePart)                  (ADR-0019)
   health/        clock-injected health tracker (bench/backoff)
   media/         image normalization to target capabilities (sniff real
                  format, downscale, transcode, byte ladder; ErrUnsupported
@@ -44,7 +49,8 @@ majordomo        Registry, Parse, env-DSN loading, chain executor, re-exports
   provider/ollama/    one native /api/chat client serving the ollama,
                       ollama-cloud, and foreman built-ins via presets
   provider/llamaswap/ llama-swap proxy: chat delegates to provider/openai,
-                      plus management methods + imagegen image client (ADR-0015)
+                      plus management methods + imagegen/audio/videogen
+                      clients (ADR-0015..0019)
   provider/google/    Gemini on google.golang.org/genai (the one approved
                       dependency; lazy client, raw-JSON-schema tools,
                       ThinkingLevel reasoning, iter.Pull2 streaming)