Select Test Mode From CLI Inputs

[drown0315]

Parent

#98

What to build

Update test command argument handling so file, directory, and no-argument
invocations select the correct execution mode. Single-file mode should preserve
existing Entry Scenario behavior and debugging options. Project Run mode should
reject ambiguous or unsupported inputs, reject --until and --print, and
prepare validated Project Scenarios before app launch.

Acceptance criteria

• flutter_pilot test <scenario.yaml> continues to run a single Entry Scenario.
• flutter_pilot test selects Project Run mode from pilot/.
• flutter_pilot test <directory> selects Project Run mode from that directory.
• Multiple positional inputs are rejected as usage errors.
• Glob-style inputs are not introduced as supported behavior.
• Single-file mode continues to allow omitted Scenario metadata.
• Project Run mode rejects --until.
• Project Run mode rejects --print.
• CLI tests cover file, directory, no-argument, multiple-input, empty-discovery, and illegal debug-option behavior.

Blocked by

• Discover Project Scenarios #99