Fix four defects the screenshots and tests exposed

Verifying the rendered pages rather than the build turned up real bugs:

- The WP-00 health page still sat at src/app/page.tsx and silently won
  the route over the new Aperçu screen, so the home page was a database
  status readout. Moved to /api/sante, where a probe belongs, and wired
  into the compose healthcheck.
- The unassigned row showed a +14 h delta against a contract of zero,
  reading as an overshoot when it is simply the volume left to staff.
  It now shows what there is to fill.
- Two sidebar entries lit at once: an anchor link matched its own page,
  and /equipe matched an employee record. Highlighting now resolves to
  the most specific match, and a test asserts exactly one entry lights
  per screen.
- Section tabs with no built screen pointed at the home page, which
  reads as a broken tab. They now lead to their first entry's
  placeholder.

Also gives truncated compliance alerts a title attribute, so a narrow
cell no longer says there is a problem without saying which.

Playwright can reuse a preinstalled browser through
PLAYWRIGHT_CHROMIUM_PATH when its revision differs from the bundled one.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Cr9dkEHwbDgkWPnyGj1Rjv

src/app/api/sante/route.ts

@@ -0,0 +1,24 @@
+import { NextResponse } from 'next/server';
+
+import { checkDatabase } from '@/server/health';
+
+export const dynamic = 'force-dynamic';
+
+/**
+ * Point de santé, destiné aux sondes de conteneur.
+ *
+ * Il ne dit que « la base répond » : ni version, ni schéma, ni compte. Une
+ * sonde est joignable sans authentification, elle ne doit donc rien apprendre
+ * à qui la interroge.
+ */
+export async function GET() {
+  const database = await checkDatabase();
+
+  return NextResponse.json(
+    { status: database.ok ? 'ok' : 'degraded' },
+    {
+      status: database.ok ? 200 : 503,
+      headers: { 'cache-control': 'no-store' },
+    },
+  );
+}

src/app/page.tsx

@@ -1,33 +0,0 @@
-import { checkDatabase } from '@/server/health';
-
-export const dynamic = 'force-dynamic';
-
-export default async function HomePage() {
-  const database = await checkDatabase();
-
-  return (
-    <main className="mx-auto flex min-h-dvh max-w-2xl flex-col justify-center gap-6 p-8">
-      <div>
-        <h1 className="text-3xl font-semibold tracking-tight">PlanFlow</h1>
-        <p className="mt-2 text-neutral-600">
-          Socle applicatif — lot WP-00. Les écrans métier arrivent aux lots suivants.
-        </p>
-      </div>
-
-      <dl className="grid gap-3 rounded-lg border border-neutral-200 bg-white p-6">
-        <div className="flex items-center justify-between gap-4">
-          <dt className="text-sm text-neutral-600">Base de données</dt>
-          <dd
-            className={
-              database.ok
-                ? 'text-sm font-medium text-emerald-700'
-                : 'text-sm font-medium text-red-700'
-            }
-          >
-            {database.ok ? 'connectée' : `indisponible — ${database.error}`}
-          </dd>
-        </div>
-      </dl>
-    </main>
-  );
-}