Move secret masking from runtime (task.go) to compile time (variables.go).
This avoids recalculating variables on each log.
- Add MaskSecretsWithExtra for loop vars and deferred commands
- Rename CmdTemplate to LogCmd (clearer intent)
- Simplify logging in runCommand
* refactor: moved/simplified snippets into its own file with tests
* refactor: move snippet to taskfile package
* feat: support snippets with line/col = 0
* feat: functional options for snippets
* feat: added option to hide snippet indicators
* feat: store raw lines for length calculations
* feat: add debug function for TaskfileDecodeError
* fix: decode errors from commands
* fix: schema for defer cmd calls
* fix: linting issues
* refactor: split var and vars into different files like other structures
