refactor(executor): add NewLocalWithConfig and replace string literals with type constants

[Soner (shyim)]

Summary

• Add NewLocalWithConfig factory function to create local executors with project and environment configuration
• Replace magic string literals in factory.go with exported type constants (TypeLocal, TypeSymfonyCLI, TypeDocker)
• Refactor NewLocal to delegate to NewLocalWithConfig for consistency
• Update CI command to use NewLocalWithConfig directly and restructure config loading
• Configure the executor in extension build/zip commands when ShopwareRoot is set

Test plan

• go test ./internal/executor/... passes
• go build ./... succeeds

[chatgpt-codex-connector]

💡 Codex Review

shopware-cli/internal/shop/config.go

Line 56 in f51918d

return env, nil

Reject nil environment entries in ResolveEnvironment

When an environment key exists but is set to null (for example environments.local: null), this function returns nil, nil instead of an error. That nil is passed to executor.New(...), which immediately dereferences cfg.Type in internal/executor/factory.go and crashes with a nil-pointer panic, turning a user config mistake into a hard process crash. Please validate env != nil before returning it and surface a descriptive config error.

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