build(deps): bump @types/node to 26.x in dev tools (split from #4587)

[epeicher]

Related issues

• Related to build(deps): bump the typescript group across 1 directory with 5 updates #4587

How AI was used in this PR

Claude Code investigated #4587, reproduced its CI failure locally, identified which half of the dependency group was safe to land, regenerated the lockfile, and ran the verification below. I reviewed the resulting diff.

Proposed Changes

Dependabot's typescript group PR (#4587) bundled a TypeScript 6 → 7 major bump together with routine @types/node updates. TypeScript 7 can't land yet: typescript-eslint hard-errors when it loads against TS 7 (Error: typescript-eslint does not support TS 7.0), and knip's peer range (typescript >=5.0.4 <7) makes npm ci fail outright — which is why every job on #4587 failed within two minutes. Upstream support is tracked in typescript-eslint/typescript-eslint#10940 and targets TS ≥ 7.1, with no timeline.

This PR takes only the part that is safe today: @types/node 25.9.3 → 26.4.0 in the two dev-only tool workspaces (tools/benchmark-site-editor, tools/compare-perf). Both are devDependencies of local tooling, so there is no runtime or user-visible impact. TypeScript stays on 6.0.3 and can be revisited once typescript-eslint supports 7.

The remaining bumps listed in #4587 (@tsconfig/node10, @types/express-serve-static-core, @types/hast) are transitive patch updates that need no manifest change and will ride along on a future Dependabot run.

Testing Instructions

Run from a clean checkout of this branch:

• npm ci — completes with no ERESOLVE error (this is the step that fails on build(deps): bump the typescript group across 1 directory with 5 updates #4587)
• npm run lint — passes (0 errors; 2 pre-existing warnings in files this PR does not touch)
• npm run typecheck — passes across all 7 workspaces

Pre-merge Checklist

• Have you checked for TypeScript, React or other console errors?

[wpmobilebot]

📊 Performance Test Results

Comparing d154941 vs trunk

app-size

Metric	trunk	d154941	Diff	Change
App Size (Mac)	1425.05 MB	1425.05 MB	+0.00 MB	⚪ 0.0%

site-editor

Metric	trunk	d154941	Diff	Change
load	1189 ms	1223 ms	+34 ms	⚪ 0.0%

site-startup

Metric	trunk	d154941	Diff	Change
siteCreation	7493 ms	7554 ms	+61 ms	🔴 0.8%
siteStartup	3372 ms	3370 ms	2 ms	⚪ 0.0%

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Results are median values from multiple test runs.

Legend: 🟢 Improvement (faster) | 🔴 Regression (slower) | ⚪ No change (<50ms diff)