docs: record that this stack-breadcrumb copy is the authoritative one

The header said where the module came from and stopped there. Accurate: it
did start as taskless/taskless's `@taskless/stack-breadcrumb` package. But
the fact a reader needs is the other one — this copy is now authoritative,
and taskless/taskless vendors it rather than maintaining its own.

Without that, nothing here tells anyone that a change made in this file
silently diverges a downstream copy, or that a fix made downstream is a fork
the next sync discards. The cloud team hit exactly that: their CLAUDE.md
credited the module to the wrong repository, and their copy's header claimed
it had been "brought into this repository" from taskless/taskless — which is
them, so the sentence had become self-referential when someone copied the
header across. They corrected their end; this is ours.

Also records why there is no drift test, since the obvious next question
after "two copies exist" is "what checks they match". Nothing does, and
deliberately: this repository moves ahead of the vendored copy by design, so
a drift test would fail on precisely the changes that are supposed to
happen. The stakes fit — a diverged breadcrumb renders a PR body slightly
differently, where a diverged rule layout writes rules to the wrong place,
which is why that one has a drift test and this one has a sentence.

Applied to the module, its test, and the workflow, because all three carry
the same origin note and a reader can arrive at any of them.

Author: theCodeDrift

.github/scripts/stack-breadcrumb.cjs

@@ -2,6 +2,16 @@
 // Adapted from the taskless/taskless stack-breadcrumb implementation
 // (@taskless/stack-breadcrumb) and brought into this repository under its MIT
 // license, with permission.
+//
+// THIS COPY IS THE AUTHORITATIVE ONE, and copies exist downstream: taskless/taskless
+// vendors it rather than maintaining its own. Fixes are made here and re-vendored
+// from here, so a change made downstream is a fork that the next sync discards.
+//
+// Nothing checks that the copies match, deliberately. This repository moves ahead
+// of the vendored copy by design, so a drift test would fail on exactly the changes
+// that are supposed to happen. The stakes suit that: a diverged breadcrumb renders a
+// PR body slightly differently, where a diverged rule layout writes rules to the
+// wrong place — which is why THAT one has a drift test and this one has a sentence.
 "use strict";
 
 /**

.github/scripts/stack-breadcrumb.test.cjs

@@ -2,6 +2,16 @@
 // Adapted from the taskless/taskless stack-breadcrumb implementation
 // (@taskless/stack-breadcrumb) and brought into this repository under its MIT
 // license, with permission.
+//
+// THIS COPY IS THE AUTHORITATIVE ONE, and copies exist downstream: taskless/taskless
+// vendors it rather than maintaining its own. Fixes are made here and re-vendored
+// from here, so a change made downstream is a fork that the next sync discards.
+//
+// Nothing checks that the copies match, deliberately. This repository moves ahead
+// of the vendored copy by design, so a drift test would fail on exactly the changes
+// that are supposed to happen. The stakes suit that: a diverged breadcrumb renders a
+// PR body slightly differently, where a diverged rule layout writes rules to the
+// wrong place — which is why THAT one has a drift test and this one has a sentence.
 "use strict";
 
 const test = require("node:test");

.github/workflows/stack-breadcrumb.yml

@@ -1,6 +1,9 @@
 # SPDX-License-Identifier: MIT
 # Adapted from the taskless/taskless stack-breadcrumb workflow and brought into
 # this repository under its MIT license, with permission.
+#
+# Authoritative here; taskless/taskless vendors this workflow and the module it
+# loads. Fixes are made in this repository and re-vendored from it.
 name: Stack Breadcrumb
 
 # Self-contained stacked-PR breadcrumb. All logic lives in a zero-dependency