build(deps): upgrade typescript to 7 and vitest to v5 (stage 2) #69

What

Part of the v2 standardization (stage 2, after stage 1 in #67/#68):

• typescript -> ^7.0.2 everywhere (root + packages).
• vitest, @vitest/* -> ^5 everywhere.
• Fix breakages (config API changes, types). Keep changes minimal and mechanical; separate commits for TS and vitest.

Why

Per AGENT_BRIEF_V2.md stage 2.

Acceptance criteria

• typescript ^7.0.2 and vitest/@vitest/coverage-v8 ^5 everywhere
• pnpm build, pnpm tsc, pnpm lint, pnpm exec oxfmt --check ., pnpm test --coverage, pnpm release:check, pnpm size all pass
• CI green