Record the QUIC README fix: the documented path failed at its first command

Two independent breaks, not one. The loader failure is fixed in CMake rather
than in prose, using an argument the build already required. The second break
fires earlier: relative cache paths resolve against the CMakeLists.txt, not
the shell, so the build died on a missing header before the loader was ever
reached.

That example was published in the same commit that deleted the working path,
and nobody ran it. Running the documentation is the check that would have
caught it, and running it is what caught it now.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

docs/typescript-quic-realtime-cut.md

@@ -864,6 +864,31 @@ the harness was deleted, and it has never worked.** A documented path that
 fails on first use is worse than no documentation: it was published in the
 same commit that removed the working one.
 
+**The README's worked example was broken twice, and fixed at `5533c34`**
+(Sonnet, on `hands/cultmath-erf`).
+
+- The loader failure above, fixed in its owner: a `POST_BUILD` step on the
+  test target copies `libmsquic.so.2` beside the built binaries. CMake already
+  receives `MSQUIC_LIB_DIR` as a required argument on Linux, so no new input,
+  option or script was invented — the knowledge it already had now acts
+  instead of sitting in prose. The `$ORIGIN` rpath is untouched.
+- **A second, independent break that fires first.** The example passed
+  `-DMSQUIC_INCLUDE_DIR` and `-DMSQUIC_LIB_DIR` as relative paths. CMake
+  resolves a relative cache path against the `CMakeLists.txt` that consumes
+  it, not the directory `cmake` ran in, so the build failed on a missing
+  `msquic.h` **before the loader problem was ever reachable**. Fixed to
+  absolute paths with a paragraph saying why.
+
+So the documented path failed at its first command, not its last. It was
+published in `796433f` — the commit that deleted the working path — and
+nobody ran it. **The check that would have caught this is running the
+documentation, which is what found it now.** Verified on Yggdrasil by
+executing the README's command block literally, with no extra step:
+`polltimeout` and `pollbusy` both pass, 20 rounds each.
+
+Structural delta: one `add_custom_command`, four lines, in the test target's
+build graph. No new files, scripts, options or targets.
+
 **Still outstanding for Cut 3:**
 
 - The **Windows release configuration**. It lived inside the harness and left