stage0: add porting guidance to CLAUDE.md

Add two points to the IP gap constraints section:
- Port functions mechanically, don't analyze individual entries first
- Time-box investigation to ~10 minutes before coding

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

stage0/CLAUDE.md

@@ -111,6 +111,15 @@ entries so that IP indices in the function body AIR match.
 - Deduplication matters. If the function body interns a value that was
   already created during module-level analysis, `ipIntern` must return
   the existing index (not create a duplicate).
+- Port **functions**, not entries. The IP entries are a consequence of
+  running the upstream functions (`createFileRootStruct`,
+  `scanNamespace`, `ensureFileAnalyzed`, etc.) correctly. Port those
+  functions mechanically from `src/Zcu/PerThread.zig` to C; do not try
+  to understand every individual IP entry before starting to code.
+- Time-box investigation. Spend at most ~10 minutes investigating a
+  problem before writing code. Use `--verbose-intern-pool` dumps to
+  verify progress after each batch, not to plan the entire
+  implementation upfront.
 
 ## AIR comparison exceptions