build(deps-dev): bump vite to 8 and typescript to 6 in /ui

[pmaxhogan]

What broke and how it was fixed

vite 6.0.0 -> 8.1.5 (ui/package.json). Build/lint/tests all pass unchanged with the existing vitest 2.1.9 + @vitejs/plugin-vue 6.0.8 (both already declare vite 8 in their peer ranges - no peer-dep incompatibility, contrary to my first guess). The only fallout was a ~0.4pp UI coverage dip: vite 8's different bundling/sourcemap output shifts which branches land as "uncovered" in a few components (AccountList.vue, SourceTable.vue, Activity.vue). Closed the gap - and then some - by adding src/__tests__/app-shell.test.ts, a smoke test for App.vue (the app shell), which had zero mount coverage before this (0% -> 98.5% on that file alone). Net UI line coverage: 88.58% -> 89.36% locally (CI's cached main baseline is 88.51%).

vitest 4.1.x is the first line that officially declares vite-8 support, and I tried it - but it switches @vitest/coverage-v8 to AST-aware remapping, which reports substantially lower (~84%) coverage on this codebase. That's not a real regression in test quality, just a stricter/more-accurate measurement, but it can't clear the CI coverage-regression gate without a baseline reset (which I can't do without merging). So the vitest bump is deliberately deferred - left a comment in vitest.config.ts explaining why, so it isn't "helpfully" redone later and silently breaks the gate.

typescript 5.6.0 -> 6.0.3 (ui/package.json). The only break was tsconfig.json's baseUrl, deprecated in TS 6 (TS5101, removed in TS 7). Removed it and converted the "@/*" path mapping to the explicit relative form ("./src/*") - TypeScript resolves paths relative to the tsconfig file when there's no baseUrl, so behavior is unchanged. vue-tsc 2.2.12 (peer range >=5.0.0) needed no bump.

telemetry-worker already pins typescript ^6.0.3 (an unrelated recent merge) and has no vite dependency at all - left untouched.

Test / gate results (all local)

• pnpm -C ui lint - 0 errors (13 pre-existing i18n key warnings, unrelated)
• pnpm -C ui run build (vue-tsc --noEmit && vite build) - passes
• pnpm -C ui run test:unit - 271/271 tests passing (29 files)
• pnpm -C ui run test:coverage - 89.36% lines (up from 88.58% on main), deterministic across 3 runs
• cargo check -p driven-app - passes

Supersedes #121 and #122.

🤖 Generated with Claude Code

[github-actions]

Coverage

Area	main	this PR	delta
Rust (lib crates)	78.70%	78.70%	+0.00 (OK)
UI (vue/ts)	88.58%	89.36%	+0.78 (OK)

Gate: passed - no coverage regression (epsilon 0.1 pp).