fix(examples): offscreen stops naming a dependency its dependency already declares

`compat.vulkan` declares `compat.vulkan-runtime` itself on Linux. Naming it here
too pinned one version in two places, in two repositories, with nothing
enforcing that they agree -- and they drifted three times in one day: the farm
moved its key, this file moved its own, and a runner holding an installed
`compat.vulkan` still recorded the previous one. Each time the build stopped
with `irreconcilable versions` and each time the repair was to edit the other
place.

Measured after removing it: the example still receives the farm --
`library_dirs` names `compat-x-vulkan-runtime/2026.09.11`, and the record reads
members 56, walked 56, no findings -- because the package that needs the
adapter is the package that says so.

The comment that explained why the adapter exists stays, and now explains why
this file does not name it.

Author: speak-agent

examples/10-graphics/offscreen/mcpp.toml

@@ -30,12 +30,21 @@ plugins = { version = "0.5.2", features = ["rules-spirv"], host-module = true }
 [dependencies.compat]
 vulkan = "1.4.357.2"
 
-# The adapter that makes the host's own ICDs reachable from a binary running
-# under mcpp's private loader. An OS predicate, which IS allowed, and a Linux
-# concern by construction: macOS resolves through dyld and Windows through the
-# PE loader, and neither has a private loader to work around.
-[target.'cfg(linux)'.dependencies.compat]
-vulkan-runtime = "2026.09.11"
+# THE ADAPTER IS NOT NAMED HERE, AND THAT IS THE POINT.
+#
+# `compat.vulkan` declares `compat.vulkan-runtime` itself on Linux -- the
+# adapter that makes the host's own ICDs reachable from a binary running under
+# mcpp's private loader, which macOS and Windows do not need because dyld and
+# the PE loader have no private-loader problem to work around.
+#
+# Naming it here as well pinned one version in two places, in two repositories,
+# with nothing enforcing that they agree. They drifted three times in one day:
+# the loader package moved its pin, this file moved its own, and an installed
+# copy of `compat.vulkan` still recorded the previous one -- each time the build
+# stopped with `irreconcilable versions`, and each time the fix was to edit the
+# other place. A dependency that another dependency already declares is a
+# second copy of a decision; the version it needs is the one that package says
+# it needs.
 
 # A Vulkan device that needs no GPU, so this example runs on a machine that has
 # none. It is a DEVICE and therefore a payload; the drivers a real GPU needs are