gitignore: ignore *.sepwork/ sep-build scratch dirs (#91)

.gitignore

@@ -1,6 +1,14 @@
 # Build outputs.
 /out/
 
+# Separate-compilation scratch dirs. `ww build` / `ww --sep` (the sole
+# build path post-#22 flip) drops <stem>.sepwork/ next to the OUTPUT
+# stem; an in-place build (no -o) lands it next to the source. The
+# Makefile byte-id gates read <stem>.sepwork/*.s deliberately (rule-10
+# #223 discriminator), so the dir is transient-not-tracked (CLAUDE.md
+# rule-14), never relocated.
+*.sepwork/
+
 # Claude Code session artifacts.
 .claude/
 .ai/