M161: Add workspace profile infrastructure

[Coasterpete]

Summary

Implements Milestone 161 by introducing workspace profile infrastructure for the Quantum editor.

Changes

• Added WorkspaceProfileId
• Added immutable WorkspaceProfile composition metadata
• Added WorkspaceProfileCatalog
• Added WorkspaceProfileManager
• Added stable pane, command-group, and overlay identifiers
• Registered Track, Train, Support, Terrain, and Simulation workspace definitions
• Kept Track as the default and only available workspace
• Integrated workspace metadata into MainWindow
• Added workspace infrastructure tests
• Added M161 documentation and updated the README

Preserved behavior

• Existing M160 workbench layout
• Route, Viewport, Inspector, Math Plots, and Diagnostics panes
• Selection synchronization
• Math Plot interaction
• Viewport rendering
• Undo/redo
• Authoring and compilation behavior
• Persistence and document state

Out of scope

• Docking
• Floating panes
• Layout persistence
• Visible workspace switching UI
• Placeholder future workspace panes
• Backend or engineering changes

Verification

• Release build succeeded with 0 warnings and 0 errors
• Full test suite passed: 1,786 tests