chore: add project documentation framework

.project-docs/00-brief/project-positioning.md

@@ -0,0 +1,29 @@
+# Project Positioning
+
+## One-line Positioning
+
+This project is {one-line project positioning}.
+
+## Primary Goal
+
+The project exists to {primary project goal}.
+
+## Target Users / Consumers
+
+- {primary user or consumer}
+
+## Non-goals
+
+This project does not aim to {non-goal or boundary}.
+
+## Core Constraints
+
+- {core constraint}
+
+## Quality Bar
+
+A good solution should {quality bar}.
+
+## Last Reviewed
+
+{YYYY-MM-DD}