fix(devcontainer): support Windows development

Use a dedicated development image so Cargo builds have the Rust toolchain, rustfmt, pkg-config, and DBus headers instead of inheriting the minimal release runtime.\n\nReplace the host HOME bind mount with named volumes for CodeWhale state and Cargo artifacts. This avoids invalid Windows HOME expansion, preserves non-root write access, and keeps Rust build churn off the workspace bind mount.\n\nDocument the Dev Container storage and rebuild behavior.\n\nVerification:\n- Built the Dev Container image with Docker Desktop\n- Verified non-root Cargo, Rust, Git, pkg-config, DBus discovery, and writable state/target paths\n- cargo build --locked\n- cargo test -p codewhale-config --locked

(cherry picked from commit 8b1ceea7f0)
Signed-off-by: Hmbown <101357273+Hmbown@users.noreply.github.com>

.devcontainer/Dockerfile

@@ -0,0 +1,29 @@
+ARG RUST_VERSION=1.88
+FROM rust:${RUST_VERSION}-slim-bookworm
+
+# Native DBus headers and pkg-config are required by libdbus-sys during
+# `cargo build`. Keep these development dependencies in the Dev Container,
+# rather than adding them to the production runtime image.
+RUN apt-get update \
+    && apt-get install -y --no-install-recommends \
+        ca-certificates \
+        git \
+        libdbus-1-dev \
+        pkg-config \
+    && rm -rf /var/lib/apt/lists/*
+
+# The official Rust image keeps its toolchain here. Preserve it after switching
+# from the image's root user to the non-root development user below.
+ENV PATH=/usr/local/cargo/bin:${PATH}
+RUN printf '%s\n' 'export PATH=/usr/local/cargo/bin:$PATH' \
+    > /etc/profile.d/codewhale-rust.sh
+RUN rustup component add rustfmt
+
+RUN groupadd --gid 1000 codewhale \
+    && useradd --create-home --shell /bin/bash --uid 1000 --gid 1000 codewhale \
+    && install -d -m 0700 -o codewhale -g codewhale /home/codewhale/.codewhale \
+    && install -d -m 0755 -o codewhale -g codewhale /home/codewhale/.cargo \
+    && install -d -m 0755 -o codewhale -g codewhale /home/codewhale/.cargo/target
+
+USER codewhale
+WORKDIR /workspaces/CodeWhale

.devcontainer/devcontainer.json

@@ -1,7 +1,8 @@
 {
   "name": "CodeWhale",
-  "dockerFile": "../Dockerfile",
   "build": {
+    "context": "..",
+    "dockerfile": "Dockerfile",
     "args": {
       "RUST_VERSION": "1.88"
     }
@@ -20,15 +21,13 @@
     }
   },
   "remoteEnv": {
-    "DEEPSEEK_API_KEY": "${localEnv:DEEPSEEK_API_KEY}"
+    "DEEPSEEK_API_KEY": "${localEnv:DEEPSEEK_API_KEY}",
+    "CARGO_TARGET_DIR": "/home/codewhale/.cargo/target"
   },
   "mounts": [
-    "source=${localEnv:HOME}/.codewhale,target=/home/codewhale/.codewhale,type=bind,consistency=cached"
+    "source=codewhale-state,target=/home/codewhale/.codewhale,type=volume",
+    "source=codewhale-cargo-target,target=/home/codewhale/.cargo/target,type=volume"
   ],
-  "features": {
-    "ghcr.io/devcontainers/features/rust:1": {},
-    "ghcr.io/devcontainers/features/git:1": {}
-  },
-  "postCreateCommand": "cargo build",
+  "postCreateCommand": "cargo build --locked",
   "remoteUser": "codewhale"
 }

docs/DOCKER.md

@@ -281,9 +281,16 @@ docker buildx build --platform linux/amd64,linux/arm64 -t codewhale .
 ## Devcontainer
 
 The repository includes a [`.devcontainer/devcontainer.json`](../.devcontainer/devcontainer.json)
-configuration for VS Code / GitHub Codespaces. It pre-installs the Rust toolchain,
-rust-analyzer, and the `codewhale` binary. Open the repo in a devcontainer to get a
-ready-to-use development environment.
+configuration for VS Code / GitHub Codespaces. It builds a dedicated development
+image with the Rust toolchain, Git, `pkg-config`, and the DBus development headers
+required by the workspace. The first open runs `cargo build --locked` and installs
+rust-analyzer and the other editor extensions.
+
+The source checkout remains mounted from the host. CodeWhale state and Cargo build
+artifacts use Docker named volumes instead, so the configuration works when VS Code
+cannot provide a POSIX-style `HOME` variable (notably on Windows), and builds do not
+write thousands of small files through a Windows bind mount. Rebuild the container
+after changing the Dev Container configuration.
 
 ## Release status