Strictly parse CLI count options

[w287346141]

Summary

• add shared integer parsers for CLI count-style options
• reject fractional, suffixed, zero, and negative values before commands run
• apply the parser to prune-sessions, events, replay, and MCP count/page options

Validation

• npm.cmd test -- --run tests/cli-number-options.test.ts tests/cli-bare-routing.test.ts tests/events-command.test.ts tests/replay.test.ts tests/update-command.test.ts
• npm.cmd run lint
• npm.cmd run typecheck
• git diff --check
• push hook ran npm.cmd run verify