feat: Add template system to weevil new command

Implements template-based project creation allowing teams to start with
professional example code instead of empty projects.

Features:
- Two templates: 'basic' (minimal) and 'testing' (45-test showcase)
- Template variable substitution ({{PROJECT_NAME}}, etc.)
- Template validation with helpful error messages
- `weevil new --list-templates` command
- Template files embedded in binary at compile time

Technical details:
- Templates stored in templates/basic/ and templates/testing/
- Files ending in .template have variables replaced
- Uses include_dir! macro to embed templates in binary
- Returns file count for user feedback

Testing template includes:
- 3 complete subsystems (MotorCycler, WallApproach, TurnController)
- Hardware abstraction layer with mock implementations
- 45 comprehensive tests (unit, integration, system)
- Professional documentation (DESIGN_AND_TEST_PLAN.md, etc.)

Usage:
  weevil new my-robot                    # basic template
  weevil new my-robot --template testing # testing showcase
  weevil new --list-templates            # show available templates

This enables FTC teams to learn from working code and best practices
rather than starting from scratch.

templates/basic/src/test/java/robot/.gitkeep

@@ -0,0 +1 @@
+# This file ensures the directory is tracked by git even when empty