docs(launcher): document hard-coded fallback path in loader resolution order

Make explicit that launch-scaffolder's third and final resolution step is
the literal path /var/mnt/eclipse/repos/standards/launcher/launcher-standard.a2ml.
This means the file's location in the standards monorepo is itself part
of the contract with launch-scaffolder, and moving/renaming it without
updating the fallback path in the loader will break every default mint.

Follow-up to f6bd5ef.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: hyperpolymath

launcher/README.adoc

@@ -17,13 +17,20 @@ specification at `docs/UX-standards/launcher-standard.adoc`.
 `launch-scaffolder` (Rust/SPARK workspace at
 `/var/mnt/eclipse/repos/launch-scaffolder/`) is the minter / provisioner /
 configurator for launchers across the estate. It consumes this standard by
-reference:
+reference, in this resolution order:
 
-* `--standard <path>` — explicit path to this file
-* `$LAUNCH_SCAFFOLDER_STANDARD` — environment-variable fallback
+. `--standard <path>` — explicit CLI argument
+. `$LAUNCH_SCAFFOLDER_STANDARD` — environment-variable override
+. `/var/mnt/eclipse/repos/standards/launcher/launcher-standard.a2ml` — the
+  hard-coded literal fallback path to this file. This is the last-resort
+  default and is why this file's location in the standards monorepo is
+  itself part of the contract: moving or renaming this file without also
+  updating the fallback path in `launch-scaffolder` will break every
+  minting operation that relies on the default.
 
 A follow-up change in `launch-scaffolder` will drop its vendored copy under
-`launch-scaffolder/standards/` and point its loader at this directory.
+`launch-scaffolder/standards/` and point its loader at this file via the
+three-step resolution above.
 
 == Sync requirement