fix(project): support running shopware-cli inside the docker dev container

[bdgraue (bdgraue)]

Follow-up to #1097, which made project create --docker / project dev work for any host UID by running the containers as the calling user. This PR covers the remaining case: running shopware-cli itself inside the dev container (directly, via an alias such as docker compose exec web shopware-cli ..., or when the CLI is shipped in the ghcr.io/shopware/docker-dev image).

Problem

Two issues surface when the CLI runs inside the container:

1. No docker to exec into. The docker-dev image ships no docker CLI, but a type: docker environment unconditionally builds a DockerExecutor. The first executor command (project storefront-build runs feature:dump) then fails with docker: not found — before any build step.
2. Unwritable HOME. Inside the container the CLI runs as the mapped host UID, which has no passwd entry, so HOME resolves to /. npm (~/.npm) and composer (~/.composer) then fail with EACCES (e.g. mkdir /.npm).

Changes

• internal/executor/factory.go — a type: docker environment falls back to local execution when running inside a container that has no docker CLI (detected via /.dockerenv / /run/.containerenv + docker not on PATH). The container is the target environment, so commands run locally. A host without docker keeps the DockerExecutor, so it still fails with a clear error instead of silently running on the host; a container with docker (dind) is unaffected.
• internal/system/home_linux.go + cmd/root.go — at startup, when HOME is unset or not writable, it is redirected to a writable temp dir, so every child process (the executor's npm/composer/console and the verifier's direct npm/node calls, which all inherit the process env) can write its caches. The writability check uses access(2) (no probe file is written, so shell completion stays side-effect free). Linux only; a no-op when HOME is already writable, so normal host and macOS/Windows usage is unchanged.

Resulting behaviour

Environment	type	docker present	inside container	Executor	HOME
Host, native	local	–	no	Local	host, no-op
Host + Docker	docker	yes	no	Docker (exec, HOME=/tmp from #1097)	unchanged
Dev container	docker	no	yes	Local (new)	redirected (new)
Container + dind	docker	yes	yes	Docker (exec)	unchanged
macOS / Windows	docker	yes	no	Docker	no-op

Testing

• New unit tests: executor fallback (local when forced, docker otherwise) and EnsureWritableHome (keeps a writable HOME, redirects when unset/unwritable).
• gofmt, go vet, go build (linux/windows/darwin), golangci-lint run ./... and go test ./... all pass.
• Verified end-to-end in the real ghcr.io/shopware/docker-dev image as UID 1001: the CLI resolves to local execution (exec: php bin/console ..., no docker: not found), redirects HOME to /tmp, and a real npm install succeeds.

Refs #1096

🤖 Generated with Claude Code

[Soner (shyim)]

Could you provide maybe an example shopware project or give access to an private one. I would like to further understand the setup 👀