Add Circle post-processing tools to TICO

[mhs4670go]

Background

Add Python-based tools for processing Circle models after export.

The long-term goal is to replace the relevant C++ tools currently provided by one-cmds with reusable Python implementations in TICO.

Circle-level transformations should remain separate from the existing ExportedProgram passes.

Initial Scope

• Circle graph optimization
• Partial graph extraction
• Model inspection and validation

Proposed Structure

tico/circle/
├── io.py
├── graph.py
├── rewrite.py
├── verify.py
├── passes/
│   ├── base.py
│   └── optimize/
├── operations/
│   └── extract.py
└── cli/
    └── main.py

The core functionality should be implemented as reusable library APIs, with thin CLI wrappers on top.