Phase 1: Stabilize legacy Pygame runtime

[sparshsam]

Objective

Stabilize the preserved Hiss-Tastic runtime without changing gameplay identity.

Scope

• Remove runtime dependency auto-install logic from hiss_tastic.py
• Preserve venv + requirements.txt workflow
• Add safer startup/error handling
• Improve runtime readability
• Preserve current gameplay behavior

Rationale

The current runtime works, but startup/install behavior and global structure make maintenance harder and less predictable.

Acceptance Criteria

• Game still launches with python hiss_tastic.py
• No auto-install behavior remains in gameplay runtime
• No gameplay mechanics intentionally changed
• README/setup instructions remain accurate
• Changelog updated appropriately

Constraints

• Do not add features
• Do not redesign gameplay
• Preserve legacy prototype identity