feat(editor): Casual Docs and Sheets editors with co-editing, comments and Office export

[tobao17]

What

Two in-app editors for the desk, both built on Casual Office (Apache/MIT):

• Casual Docs (editor_docs, .udoc): native .docx editing (ProseMirror + WASM layout), Google-Docs style header with editable title, autosave, Ctrl+S, co-editing and comments through the Casual Docs gateway.
• Casual Sheets (editor_sheet, .usheet): Univer based spreadsheet with the full Casual chrome (menus, toolbar, formula bar, comments, tables), dark/light theme, presence avatars and live co-editing through the Casual Sheets server.

Also:

• "+ New" menu gets Document / Spreadsheet rows for the new editors (same label and glyph as the ONLYOFFICE rows, Casual colours), tiles use the Casual logos.
• Download of .udoc / .usheet produces a real .docx / .xlsx (builtins/editor/export.js), like Google Docs and Sheets.
• Help menu of both editors opens a one-row "Contact us" popover that leads to the Drumee support chat.

How it is wired

• Files are stored through the existing media.save path as JSON ({docx: base64} for docs, the Univer workbook snapshot for sheets), so nothing changes server side.
• Co-editing is optional: on mount the editor probes <endpoint>/collab/health (docs) and <endpoint>/sheets/health (sheets). When the gateway is not routed the editor silently runs single-user. On stage the gateways run as Docker containers on the box and are currently routed for the liam endpoint only; the root endpoint needs the two nginx locations before co-editing is live there.
• Univer's @univerjs/docs-mention-ui is not published on npm: stubs/univerjs-docs-mention-ui provides a no-op plugin, referenced from package.json as a file: dependency.
• patches/@casualoffice+sheets+0.20.0.patch (patch-package) makes the Casual Sheets lazy plugin loader per Univer instance; upstream keeps it module global, which leaves comments and tables dead in every sheet after the first one.
• scripts/postinstall-casual.js copies the Casual Docs layout engine WASM next to the chunk that loads it (the package ships it one directory up).
• .npmrc turns on legacy-peer-deps: Casual Docs' peer ranges conflict with the Univer 0.25.1 set Casual Sheets needs. Every peer the build relies on is listed explicitly.

Verified

• Clean clone, npm install, production webpack build: 0 errors.
• On the liam stage endpoint: create, edit, save, reopen, rename, download for both editors; two-tab co-editing, remote cursors, comments with author names, presence; first click works everywhere; no periodic save loop; desk theme untouched.

Known limits

• Multi-select / zip downloads still contain the raw JSON files.
• Debug [DOCS] / [SHEET] console logs are still in place.
• Casual Docs' File menu keeps its native Open / Make a copy / Email as attachment entries.

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[sonarqubecloud]

Quality Gate failed

Failed conditions
0.0% Coverage on New Code (required ≥ 80%)
11.7% Duplication on New Code (required ≤ 3%)

See analysis details on SonarQube Cloud