fix: install bun to /usr/local/bin so it persists when /root is PVC-mounted

Dockerfile.devpod

@@ -2,7 +2,7 @@ FROM ubuntu:24.04
 
 ENV DEBIAN_FRONTEND=noninteractive
 ENV HOME=/root
-ENV PATH="/root/.bun/bin:$PATH"
+ENV PATH="/usr/local/bin:/root/.bun/bin:$PATH"
 
 # Base tools
 RUN apt-get update && apt-get install -y --no-install-recommends \
@@ -12,8 +12,9 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
     nano vim htop netcat-openbsd dnsutils iputils-ping \
     && rm -rf /var/lib/apt/lists/*
 
-# Bun
-RUN curl -fsSL https://bun.sh/install | bash
+# Bun — install to /usr/local so it's on the image filesystem, not the /root PVC
+RUN curl -fsSL https://bun.sh/install | bash -s -- --install-dir /usr/local/bin \
+    && ln -sf /usr/local/bin/bun /usr/local/bin/bunx
 
 # Claude Code CLI
 RUN curl -fsSL https://claude.ai/install.sh | bash