feat: publish conventional web extension artifacts

[peternhale]

Why

Code Builder Web expects web-compatible extensions to publish their browser bundle and runtime assets under the conventional dist/ layout. It also filters top-level out/ directories as desktop build waste.

What changed

• publish desktop and browser extension entry points under lana/dist
• resolve webview runtime assets from the same directory
• update Rollup, Rolldown, VSIX, watch, and debug configuration for the new layout
• clean intermediate log-viewer output before Rollup builds to prevent stale Rolldown chunks from entering the VSIX
• add a reproducible pnpm build:vsix target backed by the local @vscode/vsce dependency
• make pnpm serve:web launch Chromium interactively through vscode-test-web, while keeping the port-3001 server headless for Playwright E2E

Validation

• pnpm lint
• pnpm test --runInBand — 1,830 tests
• pnpm build
• pnpm build:fast
• pnpm build:vsix
• pnpm test:e2e:web — VS Code Web E2E passed
• verified the resulting VSIX contains 25 current Rollup artifacts and no stale Rolldown-only chunks
• verified the installed vscode-test-web CLI supports every interactive launcher option used by serve:web