test: add mocked crypto.subtle coverage for decryptTokenEdge (#2990)

[aaniya22]

Summary

Adds two missing test cases to test/crypto-edge.test.ts: mocking globalThis.crypto.subtle via vi.stubGlobal to verify decryptTokenEdge returns null when crypto.subtle.decrypt throws, and to assert the exact parameters passed to crypto.subtle.importKey and crypto.subtle.decrypt, per issue #2990.

Closes #2990

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Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)
• ✨ New feature (non-breaking change that adds functionality)
• 💥 Breaking change (fix or feature that changes existing behavior)
• 📝 Documentation update
• ♻️ Refactor / code cleanup (no functional change)
• ⚡ Performance improvement
• 🔒 Security fix
• 🧪 Tests only

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What Changed

• test/crypto-edge.test.ts — added two tests to the decryptTokenEdge describe block:
  • "returns null when crypto.subtle.decrypt throws" — stubs globalThis.crypto.subtle with vi.stubGlobal so decrypt rejects, and asserts the function catches it and returns null.
  • "calls crypto.subtle.importKey and crypto.subtle.decrypt with the correct parameters" — stubs crypto.subtle with spies and asserts importKey is called with "raw", a 32-byte key, { name: "AES-GCM" }, false, ["decrypt"], and decrypt is called with { name: "AES-GCM", iv: <12-byte Uint8Array>, tagLength: 128 } and the correctly-sized encrypted byte array.

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How to Test

1. Pull this branch.
2. Run pnpm install (use --ignore-scripts if the optional tree-sitter native build fails locally — unrelated to this change).
3. Run npx vitest run test/crypto-edge.test.ts.

Expected result: All 15 tests in the file pass, including the two new mocked-crypto.subtle tests.

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Screenshots / Recordings

Not applicable — test-only change, no UI impact.

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Checklist

• Linked the related issue above
• Self-reviewed my own diff
• No unnecessary console.log, debug code, or commented-out blocks
• npm run lint passes locally
• No TypeScript errors (npm run type-check)
• Added or updated tests where applicable
• Updated documentation / comments if behavior changed

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Accessibility (UI changes only)

Not applicable — no UI changes.

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Additional Context

Most of the coverage requested in #2990 (missing/invalid key, invalid hex/odd-length ciphertext, invalid IV length, successful decryption) already existed in test/crypto-edge.test.ts on main, using the real Web Crypto API end-to-end. This PR adds the two pieces the issue specifically asked for that weren't covered: mocking globalThis.crypto.subtle with vi.stubGlobal, and verifying the exact call parameters to importKey/decrypt. Flagging this so the diff's scope relative to the issue is clear.

[github-actions]

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