refactor: apply minimal tfcode branding

- Rename packages/opencode → packages/tfcode (directory only)
- Rename bin/opencode → bin/tfcode (CLI binary)
- Rename .opencode → .tfcode (config directory)
- Update package.json name and bin field
- Update config directory path references (.tfcode)
- Keep internal code references as 'opencode' for easy upstream sync
- Keep @opencode-ai/* workspace package names

This minimal branding approach allows clean merges from upstream
opencode repository while providing tfcode branding for users.

packages/tfcode/Dockerfile

@@ -0,0 +1,18 @@
+FROM alpine AS base
+
+# Disable the runtime transpiler cache by default inside Docker containers.
+# On ephemeral containers, the cache is not useful
+ARG BUN_RUNTIME_TRANSPILER_CACHE_PATH=0
+ENV BUN_RUNTIME_TRANSPILER_CACHE_PATH=${BUN_RUNTIME_TRANSPILER_CACHE_PATH}
+RUN apk add libgcc libstdc++ ripgrep
+
+FROM base AS build-amd64
+COPY dist/opencode-linux-x64-baseline-musl/bin/opencode /usr/local/bin/opencode
+
+FROM base AS build-arm64
+COPY dist/opencode-linux-arm64-musl/bin/opencode /usr/local/bin/opencode
+
+ARG TARGETARCH
+FROM build-${TARGETARCH}
+RUN opencode --version
+ENTRYPOINT ["opencode"]