fix: UTF-8 support in container vim and auto-configure origin/HEAD

- Set LANG=C.UTF-8 and LC_ALL=C.UTF-8 in Dockerfile
- Add .vimrc with UTF-8 encoding settings
- Auto-configure origin/HEAD during init project for worktree support

Author: alexsteeel

src/ai_sbx/commands/init.py

@@ -659,6 +659,32 @@ def init_project(
     except Exception:
         pass
 
+    # Set up origin/HEAD if not configured (needed for worktrees to know default branch)
+    try:
+        # Check if origin/HEAD exists
+        result = subprocess.run(
+            ["git", "symbolic-ref", "refs/remotes/origin/HEAD"],
+            cwd=project_path,
+            capture_output=True,
+            text=True,
+            check=False,
+        )
+        if result.returncode != 0:
+            # origin/HEAD not set, configure it automatically
+            set_head_result = subprocess.run(
+                ["git", "remote", "set-head", "origin", "--auto"],
+                cwd=project_path,
+                capture_output=True,
+                text=True,
+                check=False,
+            )
+            if set_head_result.returncode == 0:
+                console.print("[green]✓[/green] Configured origin/HEAD for worktree support")
+            elif verbose:
+                console.print("[dim]Could not auto-configure origin/HEAD (no remote?)[/dim]")
+    except Exception:
+        pass
+
     # Create or update project config
     if existing_config:
         config = existing_config

src/ai_sbx/dockerfiles/devcontainer-base/Dockerfile

@@ -56,8 +56,9 @@ RUN set -eux; \
     if getent group docker >/dev/null; then usermod -aG docker "$USERNAME"; fi
 
 
-# Generate locale
-RUN locale-gen en_US.UTF-8
+# Set UTF-8 environment (C.UTF-8 is available by default in Debian)
+ENV LANG=C.UTF-8
+ENV LC_ALL=C.UTF-8
 
 RUN mkdir -p /usr/local/share/npm-global && \
   chown -R $USERNAME:$USERNAME /usr/local/share
@@ -221,6 +222,7 @@ COPY --chown=$USERNAME:$USERNAME devcontainer-base/claude-defaults /home/$USERNA
 # Copy configuration files
 COPY --chown=$USERNAME:$USERNAME devcontainer-base/conf/.zshrc /home/$USERNAME/.zshrc
 COPY --chown=$USERNAME:$USERNAME devcontainer-base/conf/.tmux.conf /home/$USERNAME/.tmux.conf
+COPY --chown=$USERNAME:$USERNAME devcontainer-base/conf/.vimrc /home/$USERNAME/.vimrc
 COPY --chown=$USERNAME:$USERNAME devcontainer-base/conf/codex_config.toml /home/$USERNAME/.codex/config.toml
 
 # Create logs directory for scripts to avoid conflicts with .ai_agents_sandbox directory

src/ai_sbx/dockerfiles/devcontainer-base/conf/.vimrc

@@ -0,0 +1,13 @@
+" UTF-8 encoding
+set encoding=utf-8
+set fileencoding=utf-8
+set termencoding=utf-8
+
+" Basic settings
+set nocompatible
+set backspace=indent,eol,start
+set ruler
+set showcmd
+set incsearch
+set hlsearch
+syntax on