fix: ignore local CLAUDE.md (build + git) (#137)

A local CLAUDE.md (repo-specific Claude instructions, references the
Obsidian codemap) sits at the repo root. It's not tracked, but nothing
kept R CMD build from sweeping it into the tarball -> a "non-standard file
at top level" NOTE, same class as the stray Rplots.pdf handled in #135.

Add `^CLAUDE\.md$` to .Rbuildignore (never ship it) and `CLAUDE.md` to
.gitignore (never commit it). Verified: with CLAUDE.md present in the
source tree, the built tarball contains no CLAUDE.md.

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

Author: ehrlinger

.Rbuildignore

@@ -29,6 +29,7 @@ framed.sty
 ^CRAN-SUBMISSION$
 ^\.github$
 ^\.claude$
+^CLAUDE\.md$
 ^\.git$
 ^\.vscode$
 ^doc$

.gitignore

@@ -54,6 +54,7 @@ vignettes/uvarpro_files/
 vignettes/uvarpro.html
 
 .claude
+CLAUDE.md
 .positai
 
 # Brainstorm / visual-companion scratch