Migrate setup.py to pyproject.toml with optional extras

[krisrowe]

Problem

The repo uses setup.py instead of pyproject.toml. This is the legacy packaging format. More importantly, all dependencies (SDK, CLI, MCP) are bundled in a single install_requires — consumers who only need the SDK (e.g., to import gwsa.sdk.mail from another package) are forced to pull in Click, FastMCP, and other interface-layer dependencies they don't use.

Proposed solution

Migrate from setup.py to pyproject.toml with optional extras:

[project]
name = "gwsa"
dependencies = [
    # SDK-only dependencies
    "google-auth",
    "google-auth-oauthlib",
    "httpx",
    # ... other SDK imports
]

[project.optional-dependencies]
cli = ["click>=8.0"]
mcp = ["mcp>=1.0.0"]

This enables:

# SDK only (for cross-repo import)
pip install "git+https://github.com/krisrowe/gworkspace-access.git"

# Full install
pipx install "gwsa[cli,mcp] @ git+https://github.com/krisrowe/gworkspace-access.git"

No code changes should be required — the SDK layer already doesn't import Click or FastMCP. This is purely a packaging change. Verify by checking that no __init__.py eagerly imports from cli/ or mcp/ at package load time; if so, make those imports lazy.

See krisrowe/mcp/framework/ for the pattern documentation.

Work breakdown

• Audit gwsa/__init__.py for eager imports of cli/mcp modules
• Catalog current install_requires and split into base vs cli vs mcp
• Create pyproject.toml with optional extras
• Remove setup.py
• Verify pip install . (SDK only) works without Click/FastMCP
• Verify pip install ".[cli,mcp]" works with full functionality
• Update README install instructions
• Update any downstream repos that depend on gwsa (currently: notes uses gwsa in optional [google] extra — no change needed)