add skill

.claude/skills/port-astgen/SKILL.md

@@ -92,7 +92,7 @@ continue to Step 7 (commit progress, re-skip).
    a TODO comment describing the remaining diff.
 2. Remove ALL `fprintf`/`printf` debug statements from `astgen.c`.
 3. Remove `#include <stdio.h>` if it was added for debugging.
-4. Verify: `zig build all` must exit 0 with no unexpected output.
+4. Verify: `zig build fmt && zig build all` must exit 0 with no unexpected output.
 5. Commit:
    ```sh
    git add astgen.c astgen_test.zig

CLAUDE.md

@@ -18,3 +18,6 @@
   confirmation mid-task. If you have remaining work, continue without waiting
   for input.
 - remember: **mechanical copy** when porting existing stuff, no new creativity.
+- no `cppcheck` suppressions. They are here for a reason. If it is complaining
+  about automatic variables, make it non-automatic. I.e. find a way to satisfy
+  the linter, do not suppress it.