fix: strip selection URL fragment to prevent highlights disappearing in Firefox

[cuspymd]

Summary

• Fixes a Firefox-only bug where highlights appeared to disappear after clicking anywhere on pages that modify the URL on text selection (e.g., archive.is)
• Strips the #selection-<N>.<N>-<N>.<N> fragment from window.location.href when initializing currentUrl so highlights are always stored under the canonical base URL

Root Cause

Firefox (MV3) re-injects content scripts whenever a page changes its URL via history.pushState. Sites like archive.is append a #selection-2049.0-2049.50 fragment to the URL on text selection. This caused Firefox to re-inject the content script with the selection URL, setting currentUrl to the transient selection URL instead of the base URL. Highlights were then saved under this transient key. When the selection was cleared and the URL reverted, the content script was re-injected again with the base URL and found no highlights — making them appear to vanish (they were still in storage, just under the wrong key).

Chrome is not affected because it does not re-inject content scripts on history.pushState.

Change

// Before
const currentUrl = window.location.href;

// After
const currentUrl = window.location.href.replace(/#selection-[\d.]+-[\d.]+$/, '');

The regex only strips the archive.is-specific #selection-NNN.N-NNN.N pattern, leaving all other hash fragments (e.g., SPA route hashes like #/page) untouched.

Test plan

• Open Firefox, navigate to https://archive.is/isXfF
• Select text and create a highlight
• Click anywhere to clear the selection (URL reverts to base URL)
• Verify the highlight remains visible on the page
• Verify the highlight appears under the correct base URL in the Pages List view
• Confirm Chrome behavior is unchanged

Closes #90

🤖 Generated with Claude Code

[chatgpt-codex-connector]

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Codex Review: Didn't find any major issues. Breezy!

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