ui: add SQL to the vendored CodeMirror bundle and mount it on the SQL panes

[andyguz17]

Follow-up of #756 (drafts approved in the 2026-09-01 review). Track B — SQL Query / SQL View, step 0 of 5 (small; unblocks #839).

Summary

#753 (PR #820) vendored a CodeMirror 6 bundle (crates/ui/assets/vendor/codemirror.bundle.js, built by the documented ritual in crates/ui/vendor/codemirror/) with JSON + FHIRPath and mounted it on the View Definitions textarea (assets/vd-editor.js). The SQL Query and SQL View pages edit SQL in a plain <textarea name="sql">. Add the SQL language to the bundle and mount the editor on the SQL panes.

Requirements

1. Add @codemirror/lang-sql to crates/ui/vendor/codemirror/package.json, export it from src/entry.js on window.HfsCodeMirror, re-run the vendoring ritual and commit the rebuilt bundle. Record the new size in the vendor README (today: JSON + FHIRPath bundle; note the delta).
2. A mount script (assets/sql-editor.js, or a generalisation of vd-editor.js) that enhances textarea[name="sql"] inside the SQL library form: the textarea stays in the DOM as the form's source of truth, every change is written back (Save / Duplicate keep working as plain POSTs), the theme follows [data-theme] like the VD editor, and the editor backs out cleanly if the bundle is missing.
3. Load the bundle + script from crates/ui/templates/pages/sql-library.html only (both /ui/sql/queries and /ui/sql/views use it).
4. Dialect: SQLite. The engine is known: $sqlquery-run executes on an in-memory SQLite (rusqlite) and binds parameters as :name, which @codemirror/lang-sql's StandardSQL dialect does not recognise as a variable. Mount with the SQLite dialect so :ward highlights as in the approved design; StandardSQL and SQLDialect are exported from the bundle too, so a future engine change is a one-identifier edit, not a rebuild. (Rewritten during refinement, 2026-09-01: the original text asked for generic SQL on the assumption that the engine was unknown.)
5. No new i18n unless an aria-label is added.

Out of scope

Live run, layout, lint, completion — #839 onwards.

Acceptance criteria

• On both pages the SQL pane is a CodeMirror editor with SQL highlighting in light and dark; typing and saving round-trips the text unchanged (Rust router_http test on the POST + Playwright typing test).
• With JavaScript disabled the plain textarea works (nojs project).
• design-system.spec.ts passes; the vendor README documents the rebuilt bundle and its size.

Design reference (screenshots)

Full-page renders of the approved artboards (branch docs/756-design-references, docs/images/sql-ui-drafts/). The canvas linked above is the editable source.

SQL Query — the SQL card gets the CodeMirror editor