Stabilize engine compatibility before v1.4.0 stable

[Z3r0DayZion-install]

Context

During clean-worktree beta proof (v1.4.0-beta.1), npm ci reports transitive EBADENGINE warnings requiring Node >=20.19.0 while project baseline is 20.17.0.

Beta was allowed because all gates passed on merged main, but this must be resolved before stable.

Scope

1. Inventory all packages producing Node >=20.19.0 engine warnings.
2. Decide and document one path:
   • raise project Node baseline, or
   • pin/replace packages to remain compatible with current baseline.
3. Update engine/toolchain docs and CI matrices to match chosen policy.
4. Rerun full release gate set on chosen Node version:
   • npm test
   • npm run verify:ui
   • npm run verify
   • npm run build:wrapper
   • npm run audit:final
5. Record final decision and evidence in release-readiness docs for v1.4.0 stable.

Exit Criteria

• No unresolved EBADENGINE warnings in clean install path for the chosen stable baseline.
• Gates stay green after policy change.