feat: add cachegrind data model

internal/cachegrind/model.go

@@ -0,0 +1,26 @@
+package cachegrind
+
+// Profile holds the parsed contents of a cachegrind file.
+type Profile struct {
+	Cmd       string
+	Events    []string
+	Functions []*Function
+	ByName    map[string][]*Function // one name may appear in multiple files
+}
+
+// Function represents a single profiled function with aggregated inclusive costs.
+type Function struct {
+	Name     string
+	File     string
+	Costs    []int64 // one entry per Profile.Events; inclusive (includes callees)
+	Calls    []*Call // outgoing call edges
+	CalledBy []*Call // incoming call edges
+}
+
+// Call is a directed call edge between two functions.
+type Call struct {
+	Caller *Function
+	Callee *Function
+	Count  int64
+	Costs  []int64
+}