VS Code extension: scaffold generation with context-aware UX

[clavery]

Summary

• Adds "New from Scaffold..." command to the VS Code extension with three entry points: command palette, explorer context menu (right-click folder → B2C-DX submenu), and File → New File... menu
• Multi-step Quick Pick wizard that maps scaffold parameter types (string, boolean, choice, multi-choice) to idiomatic VS Code UI with validation, source resolution, and conditional parameter visibility
• Context-aware cartridge detection: right-clicking inside a cartridge auto-detects it, pre-fills the cartridgeName parameter, filters the scaffold list to only cartridge-targeting templates (controller, custom-api, hook, etc.), and skips the cartridge selection prompt
• Editor context: when invoked from command palette, uses the active editor's file path to detect cartridge context
• SDK: adds detectSourceFromPath() for generalized source detection from filesystem paths, exports cartridgePathForDestination(), and adds builtInScaffoldsDir option to createScaffoldRegistry() for bundled consumers
• Build: copies SDK scaffold template data into extension bundle at build time (esbuild copySdkScaffolds())

Test plan

• Right-click cartridge folder → "New from Scaffold..." → list shows only cartridge-targeting scaffolds, cartridge auto-detected, no cartridge prompt
• Right-click a subfolder within a cartridge (e.g. rest-apis/) → same behavior (walks up to cartridge root)
• Right-click non-cartridge folder → full scaffold list, prompts for cartridge
• Command palette with file open in cartridge → auto-detects cartridge context
• Command palette with no file open → prompts for everything
• File → New File... → "New from Scaffold..." appears, opens wizard with no folder context
• Press Escape mid-wizard → silently aborts
• Generate into folder with existing files → skipped files reported
• pnpm --filter @salesforce/b2c-tooling-sdk run test:agent passes
• pnpm --filter @salesforce/b2c-cli run test:agent passes