v0 plan: move given files to _files/ so go vet ./... ignores them; note the first-attempt finding

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

docs/plans/v0/_files/scripts/check-lines.sh

@@ -0,0 +1,14 @@
+#!/bin/sh
+# No Go source file over 400 lines. Reports every offender, then fails.
+set -u
+limit=400
+bad=0
+for f in $(find . -name '*.go' -not -path './.git/*' -not -path './vendor/*'); do
+    n=$(wc -l < "$f") || { echo "check-lines: cannot read $f" >&2; exit 2; }
+    if [ "$n" -gt "$limit" ]; then
+        echo "check-lines: $f has $n lines (limit $limit)"
+        bad=1
+    fi
+done
+[ "$bad" -eq 0 ] || exit 1
+echo "check-lines: ok"