chore: address PR #8985 review follow-ups

## Context

Follow-up tasks from @christian-byrne's [review](https://github.com/Comfy-Org/ComfyUI_frontend/pull/8985#pullrequestreview-3892654711) on PR #8985.

## Tasks

- [ ] **test**: Add regression test for `prompt` 5th-argument forwarding in `changeTracker.ts` ([comment](https://github.com/Comfy-Org/ComfyUI_frontend/pull/8985#discussion_r2886699341))
- [ ] **test**: Add callback execution path tests for NumberWidget prompt — invoke captured callback with test values and assert `widget.value` ([comment](https://github.com/Comfy-Org/ComfyUI_frontend/pull/8985#discussion_r2886699344))
- [ ] **refactor**: Declare `getContextMenuOptions` as optional method on `IBaseWidget` instead of duck-typing ([comment](https://github.com/Comfy-Org/ComfyUI_frontend/pull/8985#discussion_r2886699347))
- [ ] **refactor**: Extract shared `evaluateInput` → `setValue` callback in `NumberWidget` to eliminate duplication between `onClick` and `getContextMenuOptions` ([comment](https://github.com/Comfy-Org/ComfyUI_frontend/pull/8985#discussion_r2886699349))
- [ ] **fix**: Guard `safeMinMax` against `NaN` — replace `Math.abs(v) > MAX_SAFE_INTEGER` with `!Number.isFinite(v)` ([comment](https://github.com/Comfy-Org/ComfyUI_frontend/pull/8985#discussion_r2886699352))

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