Fix IPv6 link-local range check (fe80::/10) and li>button layout conflict

[Copilot]

Two bugs from the PR review: IPv6 link-local detection only covered fe80::/16 instead of the full /10 block, and li > button inherited width: 100% from the global button rule, collapsing the domain span into ellipsis.

background.js — correct link-local range

startsWith("fe80:") only matches fe80::/16; the actual link-local block is fe80::/10 (fe80–febf). Replaced with a hextet integer comparison:

// before
return bare === "::1" || bare.startsWith("fe80:") || ...;

// after
const firstHextet = bare.split(":")[0];
let isLinkLocal = false;
if (firstHextet && firstHextet.startsWith("fe")) {
  const hextetValue = parseInt(firstHextet, 16);
  if (!Number.isNaN(hextetValue) && hextetValue >= 0xfe80 && hextetValue <= 0xfebf) {
    isLinkLocal = true;
  }
}

Addresses were in fe81–febf being incorrectly treated as routable and having Accept-Language spoofing applied.

popup.css — isolate remove button sizing

li > button { flex-shrink: 0 } combined with the global button { width: 100% } caused the remove button to hold 100% flex-basis and refuse to shrink, starving the domain <span>. Added width: auto; margin: 0 to break the inheritance for in-list buttons only.

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[Copilot]

Pull request overview

This PR fixes two user-facing issues in the browser extension: (1) correctly classifying IPv6 link-local hosts as non-routable so Accept-Language spoofing is not applied, and (2) preventing list-item “remove” buttons in the popup from inheriting full-width sizing that collapses the domain label.

Changes:

• Update IPv6 link-local detection to cover the full fe80::/10 range (fe80–febf) via first-hextet parsing.
• Override global button { width: 100% } styling for li > button to avoid flex layout starvation of the domain <span>.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
background.js	Fixes IPv6 link-local range check so non-routable hosts are correctly excluded from header spoofing.
popup.css	Ensures in-list buttons size to content (not 100% width), preserving domain text visibility in the popup list.

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