feat: Implement Task Timeouts in `same.yaml`

[drlucaa]

Currently, tasks in same run indefinitely until completion or until the entire build is cancelled. We need to add support for a timeout field in the same.yaml task definition. This will allow users to specify a maximum duration for a task (e.g., 5m, 30s). If a task exceeds this limit, the system must terminate the process and report the task as failed.

Goals

• Prevent Hanging Tasks: Allow users to safeguard their builds against processes that may get stuck or hang indefinitely.
• Configuration: Provide a simple, human-readable configuration option in same.yaml.
• Enforcement: Ensure the scheduler strictly enforces these limits during execution.

Acceptance Criteria

1. Configuration & Domain

• Update the Samefile schema (internal/adapters/config/schema.go) to accept a timeout field (string).
• Update the domain.Task struct (internal/core/domain/task.go) to include a Timeout field of type time.Duration.
• Update the config loader to parse the timeout string using time.ParseDuration and populate the domain model.
• Invalid formats (e.g., "forever") should result in a config validation error.

2. Execution Logic

• Modify the Scheduler (internal/engine/scheduler/scheduler.go) to apply the timeout.
• In executeTask, if a task has a Timeout > 0, wrap the execution context using context.WithTimeout.
• Ensure that when the context deadline is exceeded, the underlying executor kills the process immediately.
• The error returned must clearly indicate a timeout occurred (e.g., wrap context.DeadlineExceeded).

3. Documentation

• Update docs/configuration/same-yaml.mdx to include the timeout field in the Task Definition section with examples.

4. Verification

• Add a unit test verifying that timeout: "10s" is correctly parsed into a duration.
• Add an integration test where a task with a short timeout (e.g., 100ms) runs a slow command (e.g., sleep 10) and asserts that it fails with a timeout error.