Fix random bound validation and harden CI

[rblake2320]

What changed

• validate secureRandomInt bounds before entering rejection sampling
• add regression coverage for zero, negative, fractional, non-finite, over-uint32, and full-domain bounds
• cancel superseded CI runs and cap the exhaustive protocol job at 60 minutes

Why

The random integer helper used a 32-bit entropy source but accepted arbitrary JavaScript numbers. A bound above 2^32 made the rejection limit zero, causing a non-terminating loop. Invalid fractional and non-finite inputs were also not rejected explicitly.

Validation

• npm run build
• npm run typecheck
• npm test
• server contract and unit suites
• npm run test:ha
• npm run test:pack
• npm audit
• git diff --check