refactor: chats method shebangs; drop chats index (D14). (#11)

Parsers and commands live in internal/chats. bin/chats/{sync,import,facts,apply}.go
are tagged shebang mains. Brain ingest is not a chats command.

internal/chats/paths.go

@@ -0,0 +1,39 @@
+package chats
+
+import (
+	"os"
+	"strings"
+)
+
+// Root locates the 2dph project root (KB_ROOT, or walk up for var/ or .git).
+func Root() string {
+	if v := os.Getenv("KB_ROOT"); v != "" {
+		return v
+	}
+	wd, err := os.Getwd()
+	if err != nil {
+		return "."
+	}
+	for i := 0; i < 10; i++ {
+		if _, err := os.Stat(wd + "/var"); err == nil {
+			return wd
+		}
+		if _, err := os.Stat(wd + "/.git"); err == nil {
+			return wd
+		}
+		parent := wd
+		if idx := strings.LastIndex(wd, "/"); idx >= 0 {
+			parent = wd[:idx]
+		}
+		if parent == wd {
+			break
+		}
+		wd = parent
+	}
+	return "."
+}
+
+// Dir is var/chats under the project root.
+func Dir() string {
+	return Root() + "/var/chats"
+}