fix(editor): bundle Monaco locally so the SQL editor works offline

[exzvor]

Summary

The SQL editor hung on "Loading…" forever for offline/closed-network users (reported via Habr, #32). @monaco-editor/react's default loader fetches the Monaco runtime from a CDN (jsDelivr) at mount time; with no network the request never resolves and every Monaco mount hangs. For a desktop SQL IDE the editor must be bundled and work offline — and "no SQL console" was a direct consequence (the console is this editor).

Fix: a side-effect bootstrap (src/lib/monaco-setup.ts), imported from main.tsx before the React tree mounts, that:

• hands the loader the locally-bundled monaco-editor (loader.config({ monaco })), and
• wires Monaco's web workers via Vite ?worker imports — the base editor.worker plus the monaco-sql-languages pgsql worker that backs SQL completion/hover.

The loader is a singleton, so this fixes every Monaco mount site (SQL editor, diff viewers, notebook, jsonb, ERD DDL preview) at once — no CDN, no network.

Related issue

Fixes #32

Tests

• npm run build — production build now emits the Monaco language/worker chunks locally (pgsql, sql, tsMode, jsonMode, lspLanguageFeatures…); main.js grows accordingly (expected: bundle replaces the runtime CDN download).
• Existing editor tests pass unchanged (MonacoEditor.test.tsx 15) — they mock @monaco-editor/react/monaco-sql-languages, so the bootstrap is untouched by them.
• Offline GUI smoke (the definitive check): run with the network disabled → the editor renders text (not "Loading…") and SQL autocomplete works; devtools Network shows zero jsdelivr/unpkg requests. Can only be confirmed in a windowed run.

Self-verification

• npm run typecheck / npm run lint clean
• npm run build green (Monaco bundled locally)
• DCO sign-off

Notes for reviewer

monaco-editor (0.55.x) resolves via the existing monaco-sql-languages dependency — no new install, lockfile unchanged. vite/client types are already enabled, so ?worker imports typecheck. Bundle-size note: the Monaco chunk is large; that's the expected, correct tradeoff for offline operation (it replaces a runtime CDN fetch). Lazy-loading the editor route could trim the initial bundle later, but that's out of scope.