Switch the equipment config (RIE / MBE / MOCVD) from the application

Start with SemiStep.UI/StartupOptions.cs:10 and SemiStep.UI/Program.cs:75 to trace config loading, culture resolution, and DI construction. Review the existing RestartPromptDialog precedent, then map the PLC sync lifecycle, open recipe, and grid surfaces before settling the mechanism, ownership, discovery, and persistence decisions. Done means the design is agreed and switching safely handles config-specific recipes and dirty-close behavior.

Intention only. Scope and mechanism are not settled; to be edited as the design firms up.

Current state

The equipment config is chosen once, before the UI exists.

StartupOptions.ConfigDir (SemiStep.UI/StartupOptions.cs:10) defaults to
C:\DISTR\Config\SemiStep\MBE and can only be overridden by the --config-dir command-line argument.
Program.StartupAsync (SemiStep.UI/Program.cs:75) loads and validates that directory, resolves the
UI culture from it, and then builds the entire DI graph — metadata registry, PLC connection settings,
grid style — before Avalonia starts. Nothing re-reads the config afterwards.

In practice, switching between RIE, MBE and MOCVD means a separate shortcut per config.

Intention

Let the operator switch the active equipment config from inside the application, rather than through
command-line arguments maintained outside it.

Open questions

• Mechanism. Relaunch the process with a new --config-dir (small; RestartPromptDialog already
  exists as precedent for the style editor), or tear down and rebuild the DI graph in place (large;
  touches the PLC sync lifecycle, the open recipe, and both grid surfaces).
• Ownership. This may belong inside the planned config-editor feature rather than standing on its
  own.
• Recipe lifetime. A recipe is config-specific — its action keys and column keys only mean
  something inside one config. Switching has to close or block on the open recipe, and a dirty-close
  guard is mandatory.
• Discovery. A fixed list of subdirectories under a configured root, or a folder picker?
• Persistence. Does the choice survive a restart, and if so, where is it written?