server: Add handling of / requests for index.html

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We expect requests ending in / to behave as they do generally on the web: if …/index.json exists, it should be served.

This ignores the hostHome concept as things are moving in another direction and that’ll become obsolete.

With this branch deployed and a card at https://minicatalog.staging.boxel.build/blog-app/BlogApp/index.json, a request for https://minicatalog.staging.boxel.build/blog-app/BlogApp/ gets a prerendered isolated response:

[github-actions]

Host Test Results

    1 files  ±  0      1 suites  ±0   1h 38m 19s ⏱️ + 9m 22s
1 887 tests +218  1 872 ✅ +220  15 💤 ±0  0 ❌  - 1 
1 902 runs  +219  1 887 ✅ +222  15 💤 ±0  0 ❌  - 2 

Results for commit ba64a27. ± Comparison against base commit 90d8c13.

This pull request removes 1 and adds 219 tests. Note that renamed tests count towards both.

Chrome ‑ Global error: Uncaught TypeError: Failed to fetch at http://localhost:7357/assets/chunk.b9c2f4bf6c1283ea8e7a.js, line 150984  While executing test: Integration | card-copy: copy button does not appear when there is 1 stack for single card item 

Chrome ‑ Integration | Store: added instance that was previously not saved will begin to auto save after being added
Chrome ‑ Integration | Store: an instance can be restored after a loader reset
Chrome ‑ Integration | Store: an instance can debounce auto saves
Chrome ‑ Integration | Store: an instance can live update thru an error state
Chrome ‑ Integration | Store: an instance live updates from indexing events for a code update
Chrome ‑ Integration | Store: an instance live updates from indexing events for an instance update
Chrome ‑ Integration | Store: an instance that started out with a local ID can be restored after a loader reset
Chrome ‑ Integration | Store: an instance will NOT auto save when its data changes, if the user does not have write permissions
Chrome ‑ Integration | Store: an instance will auto save when its data changes
Chrome ‑ Integration | Store: an unsaved instance live updates when realm event matching local ID is received
…

♻️ This comment has been updated with latest results.

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This is a test from the existing implementation of including the isolated template in index.html; when working on this I decided I didn’t like it mutating the database, and changed the setup to write files to the realm that will produce the expected boxel_index entries for inclusion in index.html.