refactor: remove the unused URL shortener

buildChatGptUrl and its fitToBudget helpers have had no production
caller since prepareAction took over routing; the 2026-10-05 plan kept
them only for existing tests until then. They also shortened silently,
against the ask-before-shortening rule, so they were a trap to reuse.

Port the tests that guard live code onto applyTemplate and
serializePrompt, including the $&, $`, $' and $$ regressions (checked to
fail against the string-replacement form), and cover prepareAction's
whole-word cut, which nothing tested before.

Also drop getContext's inputType password check. menus.OnClickData has
no inputType, so it never fired; Firefox already withholds password
fields from selectionText via mozIsTextField(true) in SelectionUtils
(bug 565717).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

lib/actions.js

@@ -13,7 +13,6 @@ const TITLES = {
 };
 
 export function getContext(info) {
-  if (info.inputType === 'password') return null;
   if (typeof info.selectionText === 'string' && info.selectionText.trim()) {
     return { kind: 'selection', source: info.selectionText.trim() };
   }