fix: prevent TypeError on undefined currentPlan.type and path-shim extname

[Copilot]

Two crash paths that produce TypeError: Cannot read properties of undefined in the renderer bundle.

mock-response-extractor.tsx — unsafe optional chain

currentPlan is loaded from localStorage as JSON.parse(... || '{}'). When no plan is cached, it is {} — truthy, so currentPlan?.type still evaluates to undefined, and calling .includes() on it throws.

// before
const isEnterprise = currentPlan?.type.includes('enterprise');

// after
const isEnterprise = currentPlan?.type?.includes('enterprise');

path-shim.ts — missing null guard

This file is the Vite path alias for the renderer bundle (vite.config.ts aliases 'path' → path-shim.ts). extname called p.lastIndexOf('.') with no guard — passing undefined throws exactly the reported error. Returns '' for falsy input, matching Node.js path.extname behaviour.

// before
export const extname = (p: string) => p.slice(p.lastIndexOf('.'));

// after
export const extname = (p: string | undefined | null) => (p ? p.slice(p.lastIndexOf('.')) : '');

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[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}