fix(vscode): ship self-contained, OS-portable .vsix via npm

[jung-thomas]

Summary

Fixes #158. The VS Code extension had three problems that made it effectively uninstallable for users:

1. No .vsix shipped in the npm package — so hana-cli vscode install fell through to instructions that pointed at a Marketplace listing that doesn't exist and a from-source build that fails.
2. Blank webviews when installed — the built .vsix loaded its Vue UI from ../app/vue/dist-vscode, a sibling path that only exists inside the repo, not in an installed extension.
3. OS-specific native binary — better-sqlite3 (a native .node module) was compiled into the bundle, so a .vsix built on one OS wouldn't load on another.

@ihenry's report was exactly this: Marketplace search returns nothing, and npm run bundle fails with dozens of Could not resolve "express" / "exceljs" / "@sap/cds" … errors — because the extension's bundle reaches into the root project's node_modules, which he hadn't installed.

Changes

Self-contained webview UI

• htmlProvider.ts: new resolveWebviewDist() prefers a local webview-dist/ (shipped in the .vsix), falls back to ../app/vue/dist-vscode for F5 dev-launch.
• esbuild.config.mjs: copies app/vue/dist-vscode → vscode-extension/webview-dist during bundle.

OS-portable — no native binary

• utils/database/index.js: default the sqlite CDS driver to Node's built-in node:sqlite (respects any explicit override). Matches the CAP 10 default; the Node >=22 baseline always ships it.
• esbuild.config.mjs: mark better-sqlite3 external so no .node binary is bundled. (Kept sqlite3 external — the build proved it's a guarded optional require in @sap/cds.)

Ship the .vsix via npm

• vscode-extension/.npmignore: allow the git-ignored *.vsix into the npm tarball while excluding all extension source.
• .github/workflows/release-hana-cli.yml: build a fresh .vsix in the publish job (installs app/vue + vscode-extension deps that root npm ci doesn't). Also fixes a latent prepack: build:vue failure — that step was added after the last successful publish and would break the next release.

Docs

• Document the root-install prerequisite for building from source (the exact #158 errors) and the offline bundled-.vsix install.

Verification

• ✅ New .vsix contains the Vue UI (301 files; the old one had 8, no UI).
• ✅ New .vsix contains zero .node native binaries.
• ✅ End-to-end: CDS connects with driver:'node', SELECT 1 runs, and better-sqlite3 is never loaded (cap-js/node-sqlite.js is).
• ✅ npm tarball ships exactly one .vsix + package.json from vscode-extension/, no source.
• ✅ eslint clean; 14 tests/utils/database.Test.js tests pass.

Notes

• node:sqlite emits an ExperimentalWarning on Node 22 (stabilizes in a later release) — expected and harmless for a dev tool, and it's the CAP 10 direction.
• The extension is still not published to the VS Code Marketplace; this PR makes the bundled-.vsix install path the reliable one.