Scenario Config and VS Code

Scenario and tool configuration are covered by spec/SPEC_0018_TOOL_CONFIG.md.

Rumoca now prefers colocated rumoca-scenario.toml files for runnable scenarios. A rumoca-scenario.toml file uses TOML content, lives next to the example it controls, and describes one task: simulation, code generation, or another explicit tool action.

VS Code should run rumoca-scenario.toml scenarios directly. The play action belongs on the scenario, not on a .mo file that requires guessing the model, source roots, solver, and viewer.

Workspace Modelica paths are visible rumoca-workspace.toml files. Keep repo-committable dependency paths there for examples. Scenario-specific paths belong in the rumoca-scenario.toml scenario.