feat(share): improve Live Share and Share Snapshot flows

[ThisIs-Developer]

Summary

• Add host-selected Live Share access modes: Can edit and View only.
• Enforce view-only Live Share participant behavior by blocking editor input, formatting commands, undo/redo, and outbound Yjs updates.
• Refresh the Live Share active-session and access-status UI.
• Update Share Snapshot with a clearer Share -> Copy flow, Live Share-style copy-link panel, footer action buttons, and custom error handling.
• Enforce Share Snapshot access mode: view-only snapshot links stay preview-only/read-only, while Can edit links open editable.
• Open Share Snapshot links in a separate tab named from the shared document title, matching the Live Share join behavior.
• Show Share Snapshot generation failures in an in-app modal and mark the link panel with a red error state.

Validation

• node --check script.js
• git diff --check
• Local browser smoke on http://127.0.0.1:8139/index.html for Live Share and Share Snapshot modal flows.

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Project	Deployment	Actions	Updated (UTC)
markdown-viwer	Ready	Preview, Comment	Jul 3, 2026 8:19pm

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