fix(migrations): load composer autoloader so run.php works on a fresh DB

run.php never loaded vendor/autoload.php. SQL migrations were fine, but PHP
migrations run as isolated subprocesses that require src/ files directly, and
those files reference sibling classes (e.g. Database -> DatabaseMigrations)
resolvable only via composer's classmap. On a fresh schema.sql database the run
died at 013_fix_remarks_keywords.php with:

  Class "DatabaseMigrations" not found in app/src/Database.php:89

- run.php now resolves and requires the autoloader (vendor/ is a sibling dir in
  dev, same-dir in prod, matching app/bootstrap.php).
- Subprocess PHP migrations get it injected via -d auto_prepend_file so each
  migration's own contract is untouched ($argv[1] stays the DB path).

Verified: fresh schema.sql DB applies 47 migrations, exit 0; second run is a
no-op (0 applied).

TODO.md

@@ -65,6 +65,7 @@
 - [x] #extend-smoke-test-for Extend smoke test for rotation and 4h idle boundary
 - [x] #fix-14-biome-check Fix 14 biome check errors: unsorted imports in scripts/css-*.mjs + unformatted CSS/JS files
 - [x] #fix-peertube-resumable-chunked-upload [!high] fix(peertube): resumable chunked upload to stop 504 on large A/V — Admin MP4 upload fails at 100%: PHP relays whole file to PeerTube via one blocking multipart POST; PeerTube edge nginx returns 504 Gateway Time-out (see xamxam-error log filepond_peertube). Migrate PeerTubeService::upload() to resumable upload protocol with chunked PATCH so no single request exceeds the proxy timeout.
+- [x] #fix-migrations-run-php-not-loading Fix migrations/run.php not loading composer autoloader (fresh-DB failure) — run.php loaded no autoloader; PHP subprocess migrations require src/ files whose sibling classes (Database->DatabaseMigrations) only resolve via composer classmap. Loaded autoloader in run.php and injected into subprocesses via -d auto_prepend_file, preserving $argv[1]=db contract. Verified: fresh schema.sql DB applies 47 migrations, exit 0, idempotent on 2nd run.
 
 ## Deferred / Blocked
 - [ ] #just-setup-backs-a [!medium] just setup backs a stale setup-dev.sh (clones php-live-reload, legacy admin/data/ dirs) — needs rewrite or removal
@@ -75,5 +76,3 @@
 - [ ] #wire-templates-to-load [!medium] Wire templates to load their page-type bundle instead of base.min.css — Update each template's <link> tags to point at the appropriate per-page bundle. Ensure no page loads CSS it doesn't need and that shared pages still get full styling.
 - [ ] #measure-before-after-css-bytes [!low] Measure before/after CSS bytes shipped per page type — Moot: part of split stream which is NO-GO (task 14). Skip unless split is revived.
 - [ ] #add-lightningcss-unusedsymbols-report-only [!high] Add lightningcss unusedSymbols report-only pass for base.min.css — SEQUENCING: do this (unusedSymbols report-only) BEFORE the per-page split (u). Reasoning: high priority, zero-risk diagnostic-only, produces reclaimable-byte go/no-go (14) against ~216KB baseline; if pruning is not worthwhile the split may not be either. Reuses inventory from v (docs/css-split-analysis.md). Start: 11 collect-content-sources.
-
-- [x] #trim-deploy-code-comments Remove oversized comment blocks from deploy-code/deploy-permissions recipes in justfile.

app/migrations/run.php

@@ -14,6 +14,33 @@
 $root = dirname(__DIR__);
 $dbPath = $argv[1] ?? ($root . '/storage/xamxam.db');
 
+// Load the composer autoloader (classmap over src/). PHP migrations require
+// src/ files directly, and those files reference sibling classes
+// (e.g. Database -> DatabaseMigrations) that are only resolvable via the
+// autoloader. Without this, run.php dies on a fresh database.
+// vendor/ is a sibling dir in dev (repo root) and same-dir in prod.
+$autoloadCandidates = [
+    dirname($root) . '/vendor/autoload.php',
+    $root . '/vendor/autoload.php',
+];
+$autoloadPath = null;
+foreach ($autoloadCandidates as $candidate) {
+    if (file_exists($candidate)) {
+        $autoloadPath = $candidate;
+        require_once $candidate;
+        break;
+    }
+}
+
+// PHP migrations run as isolated subprocesses, so they do not inherit the
+// autoloader above. Export the resolved path so run.php (and any code it
+// invokes) can inject it into those subprocesses.
+if ($autoloadPath !== null) {
+    putenv('XAMXAM_AUTOLOAD=' . $autoloadPath);
+    $_ENV['XAMXAM_AUTOLOAD'] = $autoloadPath;
+    $_SERVER['XAMXAM_AUTOLOAD'] = $autoloadPath;
+}
+
 if (!file_exists($dbPath)) {
     die("Database not found: $dbPath\n");
 }
@@ -68,9 +95,18 @@ foreach ($files as $name => $file) {
 
     try {
         if ($isPhp) {
-            // PHP migrations: execute in a subprocess for isolation
+            // PHP migrations: execute in a subprocess for isolation.
+            // The subprocess only requires the migration file, so composer's
+            // autoloader has to be loaded there too. -d auto_prepend_file
+            // injects it without altering the migration's own $argv contract
+            // ($argv[1] must remain the DB path).
+            $phpArgs = '';
+            if ($autoloadPath !== null) {
+                $phpArgs = '-d auto_prepend_file=' . escapeshellarg($autoloadPath) . ' ';
+            }
             $cmd = sprintf(
-                'php %s %s 2>&1',
+                'php %s%s %s 2>&1',
+                $phpArgs,
                 escapeshellarg($file),
                 escapeshellarg($dbPath)
             );