fix(sandbox): register /workspace as git safe directory at startup

Git refuses to operate in directories not owned by the current process
user. Since /workspace is a bind-mount owned by the host user, the UID
mismatch inside the container triggers this check. Register the path via
git config safe.directory in the entrypoint before launching OpenCode,
covering both the root (gosu) and non-root (--user) startup paths.

Author: crallen

build/entrypoint.sh

@@ -183,6 +183,13 @@ if [ "$(id -u)" = "0" ]; then
                 "${HOST_UID}:${HOST_GID}"
     preflight_checks "/home/opencode"
 
+    # --- Configure git safe directory ---
+    # /workspace is a bind-mount owned by the host user. Git refuses to
+    # operate in directories not owned by the current user, so we register
+    # /workspace as a safe directory for the opencode user. This must be done
+    # as root writing to the opencode user's gitconfig before dropping privs.
+    gosu "$TARGET_USER" git config --global --add safe.directory /workspace 2>/dev/null || true
+
     # --- Drop privileges and launch OpenCode ---
     info "Starting OpenCode..."
     # gosu replaces this process with the target user — root is gone.
@@ -203,6 +210,10 @@ info "Preparing environment..."
 sync_config "$HOME/.config/opencode" "$HOME/.config/opencode.defaults"
 preflight_checks "$HOME"
 
+# /workspace is a bind-mount that may be owned by a different UID than the
+# container user. Register it as a git safe directory so git commands work.
+git config --global --add safe.directory /workspace 2>/dev/null || true
+
 export NVM_DIR="$HOME/.nvm"
 # Source nvm.sh to enable `nvm` shell functions (e.g. `nvm install`, `nvm use`).
 # The `node` binary itself works without this via the $NVM_DIR/current symlink