fix(runtime): align idle timeout grammar

[BigDataDZ]

Summary

• replace Python str.strip() and JavaScript String.trim() with the same explicit grammar
• accept decimal digits surrounded only by ASCII whitespace
• reject NEL, File Separator, and BOM padding consistently in both runtimes
• extend the shared fixture so reverting either side to its language-native trim semantics fails parity tests

Validation

• pytest -q tests/control_plane/test_effect_runtime_integration.py — 39 passed on the real Python-to-Node path
• node --experimental-strip-types --test tests/control_plane_ts/effect_runtime_config.test.ts — 11 passed
• TypeScript control-plane typecheck — passed
• Ruff and diff hygiene — passed
• public-boundary scan — clean
• standard premerge — 9/9 selected checks passed, including 8 control-plane/canary smokes

This is a focused follow-up to loopx-project#4111 and targets its current head branch directly.