[3.x] Support custom media directories in the realtime compiler

[emmadesilva]

Summary

• pass the resolved media source and output directories from hyde serve to the server process as HYDE_SERVER_MEDIA_DIRECTORY and HYDE_SERVER_MEDIA_OUTPUT_DIRECTORY, using the existing environment plumbing
• read those in AssetFileLocator instead of hardcoding _media and media/, so a project using the media_directory config option gets its media served instead of 404s
• share the resolved output directory with the router's pre-boot fast path, keeping media requests off the framework bootstrap
• resolve dashboard media preview links through Hyde::getMediaOutputDirectory(), which was hardcoded to media/ as well

Requests that require the framework boot a fresh application, so resolved configuration cannot be shared with the pre-boot media fast path through application memory. The server process environment is where it can live instead, without paying for a bootstrap on every asset request. The defaults still apply when the server is started directly, such as through the Herd integration, where there is no serve command to resolve them.

Changing the media directory while the server is running is not picked up, since the values are resolved at startup. Restarting the server is the expected response, and this is not documented.

Tests

• realtime compiler suite: 48 passed (146 assertions), including new end-to-end coverage for serving a custom media directory and for dashboard preview links; both were confirmed to fail against the unmodified sources
• UnitFramework: 1,922 passed, with the documented PHP 8.5 FeaturedImageUnitTest failure remaining
• ServeCommand unit and feature tests: 53 passed, including a regression test that a custom media directory is resolved into the server environment
• php monorepo/HydeStan/run.php: no errors

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (573db00) to head (550cb38).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff             @@
##              master     #2587   +/-   ##
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  Coverage     100.00%   100.00%           
  Complexity      1811      1811           
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  Files            184       184           
  Lines           4494      4494           
===========================================
  Hits            4494      4494           

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[emmadesilva]

• QA result: PASS — no issues found.

• Focused tests: 99 passed; the socket-dependent Vite test also passed when rerun with network permission.
• Custom _qa-media directory served correctly at /qa-media/..., including nested files.
• Custom assets directory worked without an underscore.
• Missing assets and the old /media path returned 404.
• Dashboard generated the correct custom media link.
• hyde build copied assets to the configured output directory.
• Direct server fallback continued serving default /media/app.css.
• HydeStan reported no errors.
• Worktree is clean; temporary QA files were removed.

─ Worked for 5m 33s ───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────

gpt-5.6-luna xhigh