Add Interactive Launch Loading Panel

[drown0315]

Parent

#90

What to build

Add the interactive Target App Launch Progress experience for real terminals.
Interactive output should render a compact loading panel with an indeterminate
spinner, elapsed time, launch choices, and reliable high-level launch stage. The
panel should refresh in place and leave the successful launch summary behind
before Step progress starts.

The implementation should not show fake percentages and should not guess build
or install stages without reliable signals. When finer-grained stage detection
is not reliable, the panel should honestly show that Flutter Pilot is waiting
for the Runtime Target.

Acceptance criteria

• Interactive terminals render Target App Launch Progress as a compact in-place loading panel.
• The interactive panel includes an indeterminate spinner and elapsed time.
• The interactive panel includes launch choices from the existing launch progress data.
• The interactive panel leaves a final success summary before Step progress starts.
• Non-interactive output remains deterministic plain text without ANSI animation.
• No percentage progress is shown.
• High-level stages are shown only when supported by reliable launch information; otherwise the panel falls back to waiting for Runtime Target.
• Renderer tests cover interactive refresh behavior, spinner-compatible output, plain non-interactive fallback, and success handoff.

Blocked by

• Add Plain Target App Launch Progress #91
• Show Launch Choices And Device Selection Reason #92
• Add Launch Failure Progress Output #93