fix: make theorem workspace generation robust to source context

[kim-em]

Fixes generator failures exposed by #499.

• accept direct := sorry theorem bodies and trivia-separated := by bodies
• ignore body-like text in comments and strings
• preserve scoped syntax/notation and precise inter-declaration context for trusted helpers
• pass explicit outer variable parameters through the generated Solution delegation
• add focused regression coverage

Validation:

• lake build lean-eval test_generate
• lake exe test_generate (33 passed)
• generated and built the complete hyperbolic_viscosity workspace from Total variation estimate for hyperbolic systems #499