feat(msc-steps): add SetConfigStep for runtime config mutation

[EtienneWallet]

Summary

Adds SetConfigStep, a new step that allows users to change configuration options at runtime for the current network. This enables dynamic control of options like AUTO_GENERATE_BLOCKS mid-scene, switching between MxOps-driven block production and simulator auto-production.

Changes

Implementation

• New SetConfigStep dataclass in mxops/execution/steps/msc.py with option and value fields
• Validates option names against the current network's known options, raising UnknownConfigOption on typos to prevent silent no-ops
• New exception UnknownConfigOption in mxops/errors.py
• Exported in mxops/execution/steps/__init__.py; resolves from YAML via both SetConfig and SetConfigStep type names

Testing

• Three new unit tests in tests/test_msc_steps.py:
  • Basic config mutation (TX_TIMEOUT)
  • Block generation toggle (AUTO_GENERATE_BLOCKS) with chain_simulator_network fixture
  • Validation that unknown option names raise UnknownConfigOption
• SetConfig entry added to tests/data/all_steps.yaml to exercise the YAML factory path

Documentation

• New "Set Config Step" section in docs/source/user_documentation/steps.md with example toggle, notes on scope (current network only, process-only), string coercion caveat, and warning that only fresh-read options (e.g., AUTO_GENERATE_BLOCKS) take effect mid-scene—cached options like PROXY/PROXY_TIMEOUT cannot be changed after the network provider is instantiated
• Cross-reference added to docs/source/user_documentation/chain_simulator.md Block generation section
• Changelog entry in docs/source/dev_documentation/changelog.md
• Step counts and All Step Types list updated in CLAUDE.md (bumped to 32 types); also restored two previously-missing steps (ChainSimulatorSetState, ChainSimulatorSetTokenBalance) to the prose inventory

Testing

• Unit tests: test_set_config_step, test_set_config_step_toggles_block_generation, test_set_config_step_unknown_option_raises
• Factory instantiation test: test_instantiate_all_steps (via all_steps.yaml entry)
• Full suite: 309 tests pass
• Code quality: bandit, flake8 (max-line-length=88), ruff, pylint ≥ 9.5 all pass

Notes

• Values are strings (configparser stores strings). YAML scalars like value: false are coerced to "False" via SmartStr; documentation recommends quoting for clarity.
• Option validation is case-insensitive (option.upper() vs. get_options()) following configparser conventions.
• Only options re-read on every use (e.g., should_generate_blocks() for AUTO_GENERATE_BLOCKS) take effect mid-scene; caching of connection-level options (PROXY, PROXY_TIMEOUT) prevents runtime changes to those.
• Changes are process-only; each mxops execute run reloads the configuration from file.