fix(node): support Node 18.20.8 runtime

[John-David Dalton (jdalton)]

Note

Medium Risk
Widening the Node support matrix and changing Unicode width / process-tree sorting paths can shift behavior on older runtimes; CI only spot-checks two built modules on 18.20.8.

Overview
Lowers the supported Node floor from 24 to 18.20.8 by aligning engines.node and the package-exports nodeRange with that minimum.

Runtime code is adjusted so the build works on 18.x: findSelfNestedProcesses sorts via the existing arrayToSorted polyfill instead of Array.prototype.toSorted, and stringWidth builds its Unicode regexes through RegExpCtor (still preferring the v flag with a u fallback) so module init stays compatible across Node versions.

CI adds a post-test Node 18.20.8 step that smoke-tests the compiled dist for stringWidth and findSelfNestedProcesses.

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Engines constraints conflict on Node 18

Medium Severity

Lowering engines.node to >=18.20.8 leaves engines.npm at >=12.2.0 and engines.pnpm at >=12.12.0. npm 12 requires Node ^22.22.2, ^24.15.0, or >=26, so a Node 18.20.8 consumer cannot satisfy the full engines set. With engine-strict, install fails and the new runtime claim does not hold.

 

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