Validate operation route parameters and enforce age-appropriate topics

[llinsss]

Problem

Practice and challenge cast the raw ?op= query string to Operation without runtime validation. Visiting /game/practice?op=anything passes an unsupported value into generateQuestion(), whose switch has no default, so it returns undefined and the game crashes. Valid but age-inappropriate operations can also bypass the game hub by editing the URL.

Proposed scope

• Add a shared runtime parser/type guard for operations.
• Validate the requested operation against the active profile's age-group allowlist.
• Choose a predictable failure path: safe default with notice, or redirect to topic selection.
• Make generateQuestion() fail explicitly for invalid input rather than returning implicitly.
• Apply the same validation at every route/session entry boundary.

Acceptance criteria

• Missing, malformed, repeated, URL-encoded, and unsupported op values never crash rendering.
• Direct URLs cannot start an age-inappropriate topic without an explicit product-approved override.
• Valid operations continue to deep-link correctly.
• TypeScript enforces an exhaustive generator switch.
• Route/component tests cover all six operations and invalid inputs.

[jd5073356-max]

I've reviewed the query parameter handling issue and can implement the runtime validation layer across the game routes. My plan is to introduce a shared type guard and parser for Operation, enforce the active profile's age-group allowlist at entry boundaries, and add exhaustive type checking to generateQuestion() so invalid inputs fail explicitly without runtime crashes. I will also implement the safe fallback redirect and add full test coverage across all six operations and malformed URL scenarios. I can deliver a clean, tested PR within 2 days.

[grantfox-oss]

🦊 GrantFox — @jd5073356-max has been assigned to this issue as part of the Third Campaign campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #4)
2. Your PR will be reviewed by the DogStark maintainers

Good luck! Track your progress on GrantFox.