feat: add real-time collaborative cloud projects

[DasEric]

What & why

This PR upgrades Atelier's team cloud from manual revision-based synchronization to durable, near-real-time collaboration.

Previously, team members had to upload and download complete revisions manually. This made parallel editing difficult and could leave clients working with outdated project states.

Cloud-linked projects now use a server-authoritative live workspace:

• Local edits are converted into stable-ID, field-level operations.
• Accepted changes are broadcast automatically to connected team members.
• Additions, edits, deletions, ordering, settings, groups, drawables, tattoos, textures, and optimized assets are synchronized.
• Local changes remain responsive through optimistic updates.
• Unsent operations are stored in a durable local queue and retried after connection failures or application restarts.
• Missed WebSocket events and version gaps are recovered from an authoritative workspace snapshot.
• Binary assets are uploaded before the corresponding operation is published.
• Existing assets are reused by SHA-256; only missing or changed files are transferred.
• Cloud projects load from the live workspace even when no immutable revision exists yet.
• The manual refresh/download action now refreshes the live workspace instead of requiring headRevision > 0.
• Initial linking, uploading, cloning, and downloading display progress with phase, filename, item count, and percentage.
• workspaceVersion was added to the project schema and migration path.
• Immutable revisions remain available as explicit build and publishing checkpoints.
• An unsigned manual GitHub Actions test-build workflow was added.

The corresponding atelier-api workspace changes must be deployed before this client version is distributed.

How it was tested

Automated checks:

• bun run build
• bun run selftest:live
• bun run selftest:project
• git diff --check

Results:

• Production TypeScript/Vite build passed.
• All 8 live collaboration client checks passed.
• All 66 project schema, migration, mapping, and store checks passed.
• No diff integrity errors were found.

The real test workspace was also checked against the local API:

• 810 drawables
• 3,110 unique referenced assets
• 3,110 asset records present
• 0 missing asset records

Manual flows covered:

• Link an existing local project to a new cloud pack.
• Observe upload/check/initialization progress.
• Open the cloud project from another client.
• Download and materialize the authoritative workspace.
• Reuse already downloaded local assets.
• Apply live edits and deletions between connected clients.
• Refresh a live project without requiring a legacy revision.

Checklist

• bun run build passes
• bun run selftest:project passes
• Focused change that matches the surrounding style
• README / docs updated if behavior changed