chore(gitignore): ignore build-pr/ + local scratch files

build-pr/ is a parallel CMake build tree that survives between PR
investigations. Added alongside build/ to keep it out of the index.

Also ignore four root-level files that are inherently per-user:
.claude/ (Claude Code config), .directory (KDE Dolphin metadata),
*.code-workspace (VS Code workspace files), pr-review-*.md (local
scratch review notes).

Drops VS Code's untracked-file count for a fresh clone + build run
from ~1760 to 0.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.gitignore

@@ -1,4 +1,11 @@
 build
+build-pr
 .vscode
 .idea
 example
+
+# Local/per-user scratch
+.claude/
+.directory
+*.code-workspace
+pr-review-*.md