Add authorship note disclosing AI-assisted revisions

New subsection "A Note on Authorship and AI Assistance" at the end of
"About The Author" states that as of 19 April 2026 the author has
begun using an AI assistant as a writing and editing aid on this
book, and that all material preceding that date was produced unaided.
Points the reader at git history and the scripts/ and .github/
tooling landed around the same time as the durable markers for
distinguishing AI-assisted from unaided work going forward.

Placement rationale: "About The Author" is already the section
carrying author-identity and first-person voice, so the disclosure
lives where a reader with any interest in authorship provenance
naturally scrolls. The alternative (a Front Matter subsection) was
considered and rejected as tonally too heavy for a note that exists
mainly to answer a future question, not to front-load caveats ahead
of the book's self-description.

No test coverage applies; this is prose.

README.md

@@ -107,7 +107,7 @@ into a terminal and follow directions. Note that `gdb` is replaced by
 Then you'll need your favorite editor. We ourselves use `vi` for quick
 edits and Visual Studio Code for any heavy lifting.
 
-### How to build an assembly language
+### How to build an assembly language program
 
 We use `gcc`, the C "compiler". `g++` could also be used. On the Mac,
 `clang` can also be used.
@@ -386,6 +386,15 @@ ISAs (in chronological order):
 
 This work is dedicated to my wife Sara and sons Ian and Evan.
 
+### A Note on Authorship and AI Assistance
+
+As of 19 April 2026, Perry has begun using Claude (Anthropic's AI
+assistant) as a writing and editing aid on this book. All material
+preceding that date was produced by the author unaided. Ongoing
+AI-assisted changes are identifiable in the git history by commit
+date and by the supporting tooling introduced in [`scripts/`](./scripts/)
+and [`.github/`](./.github/) around that time.
+
 ### Gratuitous Plugs
 
 Perry has created a library of about 200 programming projects suitable