feat(deps): upgrade typescript v4→v5, @types/node v20→v22 (batch 18)

[tompahoward]

Summary

• Upgrade TypeScript from ^4.5.4 to ^5.9.3 (major version bump v4→v5)
• Upgrade @types/node from 20.10.0 (pinned) to ^22.19.15 (matching Node 22.x CI target)

Risk Rating: 2/5

Low-moderate risk. TypeScript 5 is largely backwards-compatible with TypeScript 4. Key factors:

• Zero compilation errors — clean tsc --noEmit on first try
• Build (rollup + tsc) passes without changes
• All 241 test scenarios pass (0 failures)
• Lint passes (0 errors)
• No source code changes required — only package.json and package-lock.json modified
• @types/node upgraded from pinned v20 to ranged v22, aligning with CI's Node 22.x target
• Existing tsconfig.json settings (target: "es5", moduleResolution: "node", experimentalDecorators) are fully supported in TS5

Test plan

• tsc --noEmit — clean compilation
• npm run build — rollup + tsc production build passes
• npm run lint — 0 errors (163 pre-existing warnings)
• npm run test:node-api — 241 scenarios passed
• CI pipeline — all checks (build, lint, test-node-api 20.x/22.x, duplication, dry-aged-deps, snyk)

https://claude.ai/code/session_01XdzuMzd5kWCPjJwTK6ztMd