feat: add OpenCode agent provider with DeepSeek support

- Copy opencode provider files from upstream/providers
- Add self-registration imports to host and container barrels
- Install @opencode-ai/sdk@1.4.17 in agent-runner
- Add opencode-ai@1.4.17 to container Dockerfile
- Configure .env template for DeepSeek

container/Dockerfile

@@ -22,6 +22,7 @@ ARG INSTALL_CJK_FONTS=false
 ARG CLAUDE_CODE_VERSION=2.1.128
 ARG AGENT_BROWSER_VERSION=latest
 ARG VERCEL_VERSION=52.2.1
+ARG OPENCODE_VERSION=1.4.17
 ARG BUN_VERSION=1.3.12
 
 # ---- System dependencies -----------------------------------------------------
@@ -110,6 +111,9 @@ RUN --mount=type=cache,target=/root/.cache/pnpm \
 RUN --mount=type=cache,target=/root/.cache/pnpm \
     pnpm install -g "@anthropic-ai/claude-code@${CLAUDE_CODE_VERSION}"
 
+RUN --mount=type=cache,target=/root/.cache/pnpm \
+    pnpm install -g "opencode-ai@${OPENCODE_VERSION}"
+
 # ---- ncl CLI wrapper ----------------------------------------------------------
 # Actual script lives in the mounted source at /app/src/cli/ncl.ts.
 RUN printf '#!/bin/sh\nexec bun /app/src/cli/ncl.ts "$@"\n' > /usr/local/bin/ncl && \