cmd/*_oracle: use luxcppDir() everywhere — kill all hardcoded /Users/z paths

5 oracle tools were writing KATs to hardcoded /Users/z/work/luxcpp/...
paths. All now go through the luxcppDir() helper (LUXCPP_DIR env override,
$HOME/work/luxcpp default), consistent with the lux/CLAUDE.md convention.

Also .gitignore stray oracle binaries from `go build ./cmd/<oracle>`.

.gitignore

@@ -56,3 +56,13 @@ CLAUDE.md
 GEMINI.md
 GROK.md
 QWEN.md
+
+# Stray oracle dev-tool binaries (built ad-hoc)
+/m4_*_oracle
+/cross_runtime_oracle
+/cross_runtime_verify
+/dkg_oracle
+/dkg2_oracle
+/activation_oracle
+/corona_oracle_v2
+/shamir_general_oracle

cmd/cross_runtime_oracle/main.go

@@ -77,8 +77,8 @@ func main() {
 	// hardcoded locations in luxcpp/crypto. For the cross-runtime gate
 	// we hash the canonical paths.
 	signPath := filepath.Join(*out, "sign_kat.json")
-	resharePath := "/Users/z/work/luxcpp/crypto/corona/test/kat/reshare_kat.json"
-	dkg2Path := "/Users/z/work/luxcpp/crypto/corona/dkg2/test/kat/dkg2_kat.json"
+	resharePath := filepath.Join(luxcppDir(), "crypto/corona/test/kat/reshare_kat.json")
+	dkg2Path := filepath.Join(luxcppDir(), "crypto/corona/dkg2/test/kat/dkg2_kat.json")
 
 	files := []struct {
 		name string
@@ -120,3 +120,12 @@ func main() {
 
 	fmt.Printf("wrote %s (%d entries)\n", mPath, len(m.Files))
 }
+
+// luxcppDir returns the luxcpp source root. LUXCPP_DIR overrides the default
+// of $HOME/work/luxcpp.
+func luxcppDir() string {
+	if d := os.Getenv("LUXCPP_DIR"); d != "" {
+		return d
+	}
+	return os.ExpandEnv("$HOME/work/luxcpp")
+}

cmd/m4_b_oracle/main.go

@@ -14,8 +14,9 @@
 // Bsquare = 184960669042442604975662780477 (~98-bit, fits in __uint128_t).
 //
 // Output:
-//   <luxcpp/crypto>/corona/test/kat/l2_norm.json
-//   <luxcpp/crypto>/corona/test/kat/full_rank_check.json
+//   $LUXCPP_DIR/crypto/corona/test/kat/l2_norm.json
+//   $LUXCPP_DIR/crypto/corona/test/kat/full_rank_check.json
+// (LUXCPP_DIR defaults to $HOME/work/luxcpp)
 
 package main
 
@@ -318,7 +319,7 @@ func writeJSON(path string, v any) error {
 }
 
 func main() {
-	outDir := "/Users/z/work/luxcpp/crypto/corona/test/kat"
+	outDir := filepath.Join(luxcppDir(), "crypto/corona/test/kat")
 	if err := emitL2Norm(outDir); err != nil {
 		fmt.Fprintln(os.Stderr, "l2:", err)
 		os.Exit(1)
@@ -330,3 +331,12 @@ func main() {
 	}
 	fmt.Fprintln(os.Stderr, "wrote full_rank_check.json")
 }
+
+// luxcppDir returns the luxcpp source root. LUXCPP_DIR overrides the default
+// of $HOME/work/luxcpp.
+func luxcppDir() string {
+	if d := os.Getenv("LUXCPP_DIR"); d != "" {
+		return d
+	}
+	return os.ExpandEnv("$HOME/work/luxcpp")
+}

cmd/m4_ternary_oracle/main.go

@@ -153,7 +153,7 @@ func main() {
 		})
 	}
 
-	outPath := filepath.Join("/Users/z/work/luxcpp/crypto/corona/test/kat", "ternary_sampler.json")
+	outPath := filepath.Join(luxcppDir(), "crypto/corona/test/kat", "ternary_sampler.json")
 	f, err := os.Create(outPath)
 	if err != nil {
 		fmt.Fprintln(os.Stderr, err)
@@ -168,3 +168,12 @@ func main() {
 	}
 	fmt.Fprintf(os.Stderr, "wrote ternary_sampler.json (%d entries)\n", len(out.Entries))
 }
+
+// luxcppDir returns the luxcpp source root. LUXCPP_DIR overrides the default
+// of $HOME/work/luxcpp.
+func luxcppDir() string {
+	if d := os.Getenv("LUXCPP_DIR"); d != "" {
+		return d
+	}
+	return os.ExpandEnv("$HOME/work/luxcpp")
+}

cmd/shamir_general_oracle/main.go

@@ -305,7 +305,7 @@ func main() {
 	}
 
 	outPath := filepath.Join(
-		"/Users/z/work/luxcpp/crypto/corona/test/kat",
+		luxcppDir(), "crypto/corona/test/kat",
 		"shamir_general_kat.json",
 	)
 	if err := os.MkdirAll(filepath.Dir(outPath), 0o755); err != nil {
@@ -326,3 +326,12 @@ func main() {
 	}
 	fmt.Fprintf(os.Stderr, "wrote shamir_general_kat.json (%d entries)\n", len(out.Entries))
 }
+
+// luxcppDir returns the luxcpp source root. LUXCPP_DIR overrides the default
+// of $HOME/work/luxcpp.
+func luxcppDir() string {
+	if d := os.Getenv("LUXCPP_DIR"); d != "" {
+		return d
+	}
+	return os.ExpandEnv("$HOME/work/luxcpp")
+}