V52.1: Vitest 5, measured against Vitest 4

[dapiced]

Summary

This is the first of V52's three major upgrades, each in its own PR as V44 requires: Vitest, then vite-plugin-pwa, then TypeScript 7.

Before touching anything

• I read the Vitest 5 migration guide.
• I searched the repo for every pattern it names: toThrow(''), sequential, bench, the removed vitest/* entrypoints, and vi.mock calls that are not at file top level. None were present.

Measured on the same machine and commit

	Vitest 4.1.11	Vitest 5.0.3
Unit tests	924 passed	924 passed, unchanged
Statements / branches / functions / lines	64.93 / 53.94 / 54.46 / 66.06 %	64.92 / 53.94 / 54.46 / 66.05 %
test:coverage, 3 runs	124–143 s	131–134 s
vitest run	82–86 s	85–87 s

Changes that could have shifted results silently, and what happened

• clearMocks now defaults to true. All tests still pass, so none relied on mock calls accumulating across tests.
• Coverage include/exclude paths are now resolved relative to the project root. The numbers move only by rounding: the statement count drops by five. Every V49 coverage floor is still met.

Node version

• Vitest 5 requires Node 22.12 or later. engines goes from >=20 to >=22.12, and the README says so.
• CI and .nvmrc already use Node 22.

Docs

• The site docs do not mention Vitest or Node, so nothing changes there.
• PLAN.md gets a V52.1 row. CHANGELOG.md is regenerated and the version becomes 1.52.0.

Test plan

• npm run test:coverage: 924 passed, all floors met
• lint, typecheck, format:check, build
• npm audit gates (prod high, all critical): clean
• CI

🤖 Generated with Claude Code

https://claude.ai/code/session_01ELAjHYDyxa5zbbdcke1bMA

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