refactor: unify the toolchain on Vite+ (vp)

[ubugeeei]

Replaces the split oxlint/vitest/vite setup with the Vite+ toolchain and moves tool configuration into vite.config.ts.
Toolchain

• Adds vite-plus (0.2.7); vite becomes a workspace catalog alias for @voidzero-dev/vite-plus-core, so plugins keep resolving vite as before.
• Scripts call vp lint / vp test / vp build; pnpm still drives the recursive orchestration, so pnpm lint, pnpm build and pnpm test keep their meaning and CI needs no changes -- vp comes from node_modules/.bin.
• vitest imports rewritten to vite-plus/test, vitest/config to vite-plus. No formatting changes: the repo is not oxfmt-clean, so check.fmt is false and vp check runs lint only. Configuration
• .oxlintrc.json moves into the lint block of a new root vite.config.ts, rules and comments intact. vp lint reports the same 0 errors / 64 warnings.
• Every vitest*.config.ts folds into its package's vite.config.ts. The two packages that ran two suites (workshop-backend, gatekeeper-scheduler) now use test.projects instead of a second config file and a second vitest call. TypeScript 7
• Most packages move to TypeScript 7. It has no JS compiler API -- the npm package exports version and nothing else -- so code that drives the API uses a typescript-5 alias, and workshop-frontend/workshop-backend/ gatekeeper-scheduler stay on 5.9 (capnweb's recursive Stub types exceed tsgo's instantiation depth; capnweb-validate builds a ts.Program).
• tsgo requires explicit rootDir under declaration emit and drops baseUrl. baseUrl is removed from 21 tsconfigs (their paths were already relative). The 17 packages that compile sibling-package sources get noEmit: true -- nothing consumes their dist, and AGENTS.md already describes pnpm build as a type check -- and the 5 that only compile their own src get rootDir. Known gap: vp test does not yet work for workshop-backend and gatekeeper-scheduler. Under Vite+ their @cloudflare/vitest-pool-workers suites fall back to Node's vm instead of workerd. Bumping the pool to 0.20.2 does not help. Every other package's tests pass, as do pnpm build and pnpm lint.

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[ndisidore]

Thanks for your interest and contribution! We have our own upgrade process in the works and are putting careful thought into introducing new dependencies