Fix basedpyright type errors and re-enable type checking

[corv89]

Summary

• Fix all 97 basedpyright type errors (reduced to 0)
• Re-enable type checking in pre-commit hooks and CI workflow
• Create shared execute.py module for sandbox execution

Changes

New Files

• shannot/_protocols.py - Protocol types for mixin pattern typing
• shannot/execute.py - Shared sandbox execution function for CLI and MCP server

Type Fixes

• Add FSObject.kind attribute and fix method signatures in mix_vfs.py
• Fix Optional type annotations across approve.py, ssh.py, mix_remote.py
• Use TYPE_CHECKING for platform-specific struct definitions in structs.py
• Add type: ignore comments for mixin attribute accesses
• Fix set.extend() → set.update() bug in interact.py
• Add None checks and class attribute annotations in test files
• Update MCP server to use shared execute_script() function

CI/Pre-commit

• Re-enable basedpyright in .pre-commit-config.yaml
• Remove continue-on-error: true from type checker step in test.yml

Test plan

• All 121 unit tests pass
• uv run basedpyright reports 0 errors
• Pre-commit hooks pass

[github-actions]

❌ CHANGELOG.md is out of date

Please update the changelog by running:

make changelog

Or manually:

git-cliff --config cliff.toml -o CHANGELOG.md

Then commit the updated CHANGELOG.md file.

[github-actions]

❌ CHANGELOG.md is out of date

Please update the changelog by running:

make changelog

Or manually:

git-cliff --config cliff.toml -o CHANGELOG.md

Then commit the updated CHANGELOG.md file.

[github-actions]

❌ CHANGELOG.md is out of date

Please update the changelog by running:

make changelog

Or manually:

git-cliff --config cliff.toml -o CHANGELOG.md

Then commit the updated CHANGELOG.md file.

[github-actions]

❌ CHANGELOG.md is out of date

Please update the changelog by running:

make changelog

Or manually:

git-cliff --config cliff.toml -o CHANGELOG.md

Then commit the updated CHANGELOG.md file.