feat: Implement Global Tool Configuration via `.same/config.yaml`

[drlucaa]

Currently, the behavior of the same CLI is primarily driven by task-specific configurations in same.yaml or workspace-wide settings in same.work.yaml. We need to introduce a dedicated global configuration file located at .same/config.yaml to control the tool's internal behavior.

The first priority for this configuration is version validation. This will allow teams to pin a specific version of the same binary for a project. If a developer runs the project with a different version of the CLI, the tool should issue a warning to ensure consistency across environments, fulfilling our brand promise of reliability and determinism.

Goals

• Establish a pattern for global tool configuration following Clean Architecture principles.
• Provide a mechanism to enforce or suggest specific CLI versions for a repository.
• Ensure the configuration is discoverable in both standalone and workspace modes.

Acceptance Criteria

1. Configuration Loading

• The CLI must attempt to load .same/config.yaml during initialization.
• In a workspace setup, the file should be searched for relative to the workspace root defined in same.work.yaml.
• In standalone mode, it should be searched for in the .same directory relative to the same.yaml.
• The configuration must be unmarshaled into a new SameConfig domain model.

2. Version Validation logic

• The config.yaml must support a top-level version field (e.g., version: "0.1.0").
• The tool must compare this value against the internal build.Version.
• If the versions do not match, a warning must be printed to stderr using the standard logger.
• The CLI must continue execution after the warning (non-breaking validation).

3. Technical Standards

• Implementation must use go.trai.ch/zerr for any loading errors.
• The loading logic must be added as a port in internal/core/ports and implemented in internal/adapters/config.
• All new logic must be verified with nix develop -c go test -race ./cli/....
• Documentation in docs/ must be updated to include the new configuration file schema.