Show "No results found." instead of an endless loading message

[ZeldaZach]

Fixes #709

Problem

DownloadList.vue used one condition to represent two different states:

div(v-if="resultsTotalLength === 0")
  p.results-message Loading...

resultsTotalLength starts at 0 and is also 0 when a search matches nothing, so filtering All Sets or All Decks by something like "blah blah blah" left the page stuck on "Loading..." forever.

Changes

• Loading is now derived from the fetched data itself (isLoading = defaultList.length === 0), and an empty result set gets its own No results found. message.
• Counts are seeded by a watch on defaultList with immediate: true rather than onMounted. SetList/DeckList are fetched in Layout.vue's onMounted, so the old hook read an empty array on every load.
• DownloadSorter.vue watches props.list and re-applies the active search/filters when the data lands. Its only prior onHandleChange call was a 300ms timeout fired at mount, which raced the API response.

Testing

eslint clean on both components, vitepress build succeeds, and the jest suite passes (26 tests). The interaction itself was not driven in a browser.

🤖 Generated with Claude Code

https://claude.ai/code/session_01Xba7S7uYsrKAVdniqNcfhS

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (5d085ec) to head (e93abc4).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #730   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            1         1           
  Lines           69        69           
  Branches        27        27           
=========================================
  Hits            69        69           

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