Add comprehensive test coverage for bookmarks, crypto, and signaling

[pheuberger]

Summary

This PR adds extensive test coverage for three critical service modules: bookmark validation, cryptographic conversions, and WebSocket signaling. The new tests ensure data integrity across encryption pipelines, proper message routing, and robust bookmark handling.

Key Changes

Bookmarks Service Tests (bookmarks.test.js)

• Inbox items: Added 5 tests validating that inbox items can have empty/missing titles while regular bookmarks require titles
• Favicon and preview fields: Added 4 tests ensuring these optional fields are properly passed through or default to null
• Tag edge cases: Added 4 tests covering non-string values, non-array inputs, trimming/lowercasing, and deduplication behavior
• URL normalization edge cases: Added 4 tests for encoded characters, multiple query parameters, internationalized domains, and very long paths

Crypto Conversion Utilities Tests (crypto-conversions.test.js) - NEW FILE

• Base64 conversions: 6 tests validating base64↔Uint8Array/ArrayBuffer conversions with edge cases (empty, padding, all byte values 0-255)
• Round-trip integrity: 8 tests ensuring data survives multiple encoding/decoding cycles (critical for encrypted data)
• Cross-function compatibility: 4 tests verifying string→buffer→base64→buffer→string pipelines work correctly
• Random byte generation: 4 tests validating cryptographic randomness and proper Uint8Array returns
• 284 total lines covering the exact conversion paths used in encryption operations

Signaling Service Tests (signaling.test.js) - NEW FILE

• Utility functions: 3 tests for getPairingRoomName and getSignalingUrl helpers
• SignalingClient initialization: 8 tests verifying proper default state (disconnected, empty subscriptions, no pending messages)
• Subscription management: 6 tests for subscribe/unsubscribe with multiple callbacks and topics
• Message publishing: 4 tests covering queuing behavior when disconnected and direct sending when connected
• Message routing: 10 tests ensuring messages reach correct topic subscribers, handle malformed JSON, and prevent callback errors from crashing others
• Connection cleanup: 7 tests validating close() properly clears state and can be called multiple times
• WebSocket state handling: 5 tests for _send() respecting WebSocket readyState
• Integration tests: 3 tests verifying subscribe→unsubscribe→handleMessage workflows
• 599 total lines with deterministic, non-flaky tests avoiding real WebSocket connections

Notable Implementation Details

• Crypto tests focus on the exact byte sequences used in AES-256 encryption (32-byte keys, 12-byte IVs) to catch silent data corruption
• Signaling tests use mocked WebSocket instances and vi.fn() callbacks to test pure logic without timing dependencies
• All tests are deterministic and can run in any order without side effects
• Tests document the critical paths: encryption round-trips, message routing, and subscription lifecycle

https://claude.ai/code/session_014P4FqiX28FYRq7h2V4Dves

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