feat(generate): add workspace asset library

[DrHepa]

Summary

Adds a Workspace Asset Library to the Generate area so users can browse indexed workspace outputs and safely reopen supported assets without touching the viewer implementation.

What changed

Electron registry / IPC / preload

• Adds an Electron-side artifact registry service that indexes workspace assets under supported workspace roots.
• Adds structured list/read/open results for renderer-safe consumption.
• Wires workspace library IPC handlers.
• Adds a scoped preload API for workspace library list/read/open calls.

Shared contracts

• Adds shared Workspace Asset Library types for entries, capabilities, source scopes, openability, read/open requests, structured errors, warnings, manifests, source links, and provenance-style metadata.
• Adds lightweight artifact/source metadata types used by the library boundary.

Renderer projection / service

• Adds renderer projection that normalizes registry entries into UI-safe entries.
• Supports open targets: self, linked-source, and unavailable.
• Adds fail-closed handling for unsupported or unsafe assets.
• Adds a renderer service wrapper that validates read/open requests before crossing IPC.

GeneratePage UI

• Adds a Library button and popover in Generate.
• Supports refresh, search, sorting, grouped/collapsible display by source scope and capability, selection, open status messaging, and safe open behavior.
• Preserves the existing Generate open/job flow instead of introducing a new viewer-state model.

Safety / path validation

• Restricts registry access to allowed workspace-relative paths.
• Rejects unsafe workspace paths, self-links, mismatched source links, Windows absolute paths, and UNC paths.
• Keeps unsupported entries visible but unavailable rather than throwing or opening unsafe paths.

Tests

• Adds focused tests for shared types, Electron registry behavior, IPC/preload wiring, renderer projection/service behavior, UI helper behavior, linked-source opens, and Windows/UNC path rejection.

Explicit non-goals

• No direct Viewer3D changes.
• No private viewer-state stack or viewer-side artifact tooling is introduced.
• Advanced .ply/.splat viewer opening remains out of scope unless routed through safe supported sources.

Changed areas

Area	Files
Electron registry/IPC/preload	electron/main/artifact-registry-service.ts, electron/main/ipc-handlers.ts, electron/preload/electron-api.ts, electron/preload/index.ts
Shared contracts	src/shared/types/assetLibrary.ts, src/shared/types/artifacts.ts, src/shared/types/electron.d.ts
Renderer services/projection	src/areas/generate/assetLibraryProjection.ts, src/areas/generate/assetLibraryService.ts, src/areas/generate/assetLibraryUi.ts
Generate UI	src/areas/generate/GeneratePage.tsx
Tests	*.test.ts files added for all new boundaries

Test plan

• node --test --experimental-strip-types src/shared/types/assetLibrary.test.ts src/areas/generate/assetLibraryProjection.test.ts src/areas/generate/assetLibraryService.test.ts src/areas/generate/assetLibraryUi.test.ts electron/main/artifact-registry-service.test.ts electron/preload/artifact-registry-preload.test.ts
• npm test
• Confirmed PR diff has no src/areas/generate/components/Viewer3D.tsx changes
• Manually validated the Workspace Library flow on Windows in a clean upstream/dev-based worktree

Review notes

This PR is intentionally scoped to Workspace Library only. It does not include the separate ViewerAuthoringHost/Phase 1B work so the diff remains focused and reviewable.