fix(ci): redirect mise cache to rootless user home in e2e

With mise now discoverable and runnable, 'mise run' still failed with
'Permission denied (os error 13)' at src/lock_file.rs:37. The CI image sets
MISE_CACHE_DIR=/opt/mise/cache (root-owned), which the openshell-test user
inherits but can only read (a+rX), not write. mise must write tool bin-path
caches (/opt/mise/cache/<tool>/.../bin_paths-*.msgpack) and task lock files
(/opt/mise/cache/lockfiles/*) even with --skip-deps.

Override MISE_CACHE_DIR to the rootless user's home so mise has a writable
cache, keeping the shared /opt/mise tool data dir read-only. The state dir
already defaults to the user's home; MISE_DATA_DIR stays inherited so the
prebuilt toolchain is reused.

Verified locally against ci:latest with CI=true (which makes mise auto-trust
the config, matching CI): the task now renders and runs into
e2e/rust/e2e-podman-rootless.sh with no permission or trust errors.

Signed-off-by: Piotr Mlocek <pmlocek@nvidia.com>

Author: pimlock

.github/workflows/e2e-test.yml

@@ -114,6 +114,7 @@ jobs:
               PATH="/root/.cargo/bin:/root/.local/bin:/opt/mise/shims:/opt/mise/bin:${PATH}" \
               CARGO_HOME="/root/.cargo" \
               RUSTUP_HOME="/root/.rustup" \
+              MISE_CACHE_DIR="/home/openshell-test/.cache/mise" \
               OPENSHELL_SUPERVISOR_IMAGE="${OPENSHELL_SUPERVISOR_IMAGE}" \
               OPENSHELL_REGISTRY="${OPENSHELL_REGISTRY}" \
               OPENSHELL_REGISTRY_HOST="${OPENSHELL_REGISTRY_HOST}" \