ci(devcontainer): skip FUSE and fs-error tests in Codespaces

Replace --device=/dev/fuse, --cap-add=SYS_ADMIN, and apt-installed FUSE
packages with RUSTFLAGS that skip the cross-device and fs-errors tests.
FUSE mounts fail with permission denied in Codespaces even with the
device exposed and SYS_ADMIN capability.

https://claude.ai/code/session_01LfpnUZrgq93MVZgA3KVqE6

Author: claude

.devcontainer/devcontainer.json

@@ -1,10 +1,9 @@
 {
   "name": "parallel-disk-usage (Rust only)",
   "image": "mcr.microsoft.com/devcontainers/rust:1",
-  "runArgs": [
-    "--device=/dev/fuse",
-    "--cap-add=SYS_ADMIN"
-  ],
+  "remoteEnv": {
+    "RUSTFLAGS": "--cfg pdu_test_skip_cross_device --cfg pdu_test_skip_fs_errors"
+  },
   "customizations": {
     "vscode": {
       "extensions": [

.devcontainer/full/devcontainer.json

@@ -1,10 +1,9 @@
 {
   "name": "parallel-disk-usage (full)",
   "image": "mcr.microsoft.com/devcontainers/rust:1",
-  "runArgs": [
-    "--device=/dev/fuse",
-    "--cap-add=SYS_ADMIN"
-  ],
+  "remoteEnv": {
+    "RUSTFLAGS": "--cfg pdu_test_skip_cross_device --cfg pdu_test_skip_fs_errors"
+  },
   "features": {
     "ghcr.io/devcontainers/features/node:1": {
       "version": "lts",

.devcontainer/full/post-create.sh

@@ -1,9 +1,6 @@
 #!/usr/bin/env bash
 set -euo pipefail
 
-echo "Installing external test dependencies..." >&2
-sudo apt update && sudo apt install -y squashfs-tools squashfuse fuse3
-
 echo "Installing Python dependencies..." >&2
 python3 -m pip install --user toml
 

.devcontainer/post-create.sh

@@ -3,9 +3,6 @@ set -euo pipefail
 
 mkdir -p "$HOME/.local/bin"
 
-echo "Installing external test dependencies..." >&2
-sudo apt update && sudo apt install -y squashfs-tools squashfuse fuse3
-
 bash "$(dirname "$0")/install-rust-toolchain.sh"
 bash "$(dirname "$0")/install-hyperfine.sh"