Duplicate permission prompts in the same second are not deduplicated

Summary

Identical permission prompts arriving within the same second are not deduplicated. Each one blocks independently, multiplying the stall time.

Evidence

• 141 groups of duplicate prompts in the same second
• Worst case: 5 identical prompts in a row
• Example: two external_directory prompts for the same path at 19:18:29, within 0.5 seconds of each other
• This doubles the wait time — answer one prompt, another identical one is still blocking
• 48.9% of all 3270 prompts are repeats across sessions (persistence bug); within single session, duplicates add extra overhead

Expected behavior

If a permission prompt is already pending for an identical (action, resource, session) combination, skip or merge the duplicate.

Version: 1.18.16, Electron 42.3.3