Second routing probe: an explicit .html file per code

Directory indexes fall back to the root page, but files with an extension are
served directly. If this resolves, per-video pages with real Open Graph tags in
the head are possible on a static host, at the cost of five characters.

v/probe123.html

@@ -0,0 +1,7 @@
+<!doctype html>
+<html><head>
+<meta charset="utf-8">
+<title>FILE PROBE</title>
+<meta property="og:title" content="file probe og title">
+</head>
+<body><p>explicit html file routing works</p></body></html>

v/probe123/index.html

@@ -1,8 +1 @@
-<!doctype html>
+removed
-<html><head>
-<meta charset="utf-8">
-<title>ROUTING PROBE</title>
-<meta property="og:title" content="probe og title">
-<meta property="og:image" content="https://example.com/probe.jpg">
-</head>
-<body><p id="probe">directory-index routing works</p></body></html>