feat: Export Data UI (browser download) + UI static MIME fix

[jung-thomas]

Summary

Adds an Export Data UI to the hana-cli web app (hana-cli ui), mirroring the existing hana-cli export CLI command and delivering the result as a browser download. Also fixes a blank-page/MIME bug in the UI static route, and folds in two pre-existing local changes (a schema-propagation fix and VSCode extension packaging).

Export UI (main feature)

• New Export view in the sidebar — the "Import / Convert" group is relabeled "Import / Export / Convert" and gains an Export entry beside Import and Mass Convert.
• GET /hana/export route streams the query result back as a file attachment (CSV / Excel / JSON), following the existing /excel route pattern.
• Shared serializers — the CSV/Excel/JSON serializers in bin/export.js are refactored into pure buffer-returning functions used by both the CLI and the new route (one source of truth).
• hana-cli exportUI launcher — opens the browser directly on the Export screen (mirrors importUI).
• Options exposed: table, schema, format, columns, limit, and CSV delimiter / include-headers / null-value.

Security

where and orderby were intentionally not implemented (an automated security review flagged raw SQL fragments; they were removed rather than hardened). Identifier inputs (schema, table, each columns entry) are validated with the project's sqlInjection.isAcceptableParameter() guard before any DB connection, and limit is integer-validated (rejects < 1). A final whole-branch review fuzzed the guard (~25 payloads) and found no residual injection surface.

Also included

• fix(ui): blank page / MIME error — the SPA catch-all served index.html (as text/html) for missing /ui/* assets after a rebuild, so browsers rejected the HTML as a JS module. The fallback now 404s for paths with a file extension, and index.html is served no-cache so new asset hashes are always picked up. Regression tests added.
• fix(connections): propagate HANA_CLI_SCHEMA — in the MCP/VSCode direct-connection path the container schema wasn't propagated, leaving CURRENT_SCHEMA empty so schema-filtered commands (tables, views, …) returned no rows. Now set on connect (and cleared on connection switch). Regression tests added.
• chore(vscode): packaging — adds a package:vscode npm script, bumps the extension to 0.1.1 and sap-hdb-promisfied to 2.202607.1.

Testing

• All 70 tests covering the changed code pass: export serializers (9), export route incl. success paths via esmock (9), static route (11), connections (39), alias-conflict guardrails (2).
• Vue app type-checks (vue-tsc) and builds cleanly.
• ⚠️ Not run: the live end-to-end download against a real HANA database (no live connection in this environment). The route is covered by mocked-DB tests, but the real download flow has not been manually exercised.
• Note: the full npm test run shows 25 pre-existing failures in environmental E2E/UI tests (server-launch-with-browser, wdio browser global, live-DB systemInfo assertions). This branch modifies none of those test files; they fail independently of these changes.

Design & plan docs

• Spec: docs/superpowers/specs/2026-07-13-export-ui-design.md
• Plan: docs/superpowers/plans/2026-07-13-export-ui.md