docs: clarify existing project adoption (#147)

Author: roian6

README.md

@@ -87,9 +87,11 @@ The wizard auto-detects which harnesses you have (OpenCode, Pi, or both), adds t
 
 ### Adding Magic Context to an existing project
 
-Magic Context is not limited to greenfield work. Run the setup wizard from the root of the project you already use with OpenCode or Pi, then restart the harness in that same directory so the plugin can attach to the existing project identity. New turns will be captured automatically, and older raw session history is summarized as the historian runs.
+Magic Context is not limited to greenfield work. Run the setup wizard from the root of the project you already use with OpenCode or Pi, then restart the harness in that same directory so the plugin can attach to the existing project identity. From that point forward, new turns are captured automatically and the historian compartmentalizes the active session as it grows.
 
-If you want to start organizing existing knowledge right away, use `/ctx-recomp` after setup to rebuild compartments from available history and `/ctx-dream` to run dreamer maintenance on demand. The dashboard can also inspect the shared CortexKit database, memories, compartments, and dreamer runs without starting a coding session.
+Magic Context does **not** retroactively import or reprocess OpenCode or Pi sessions that happened before it was installed. Those past conversations are not backfilled into compartments. What builds up across an existing project from day one includes project memories, dreamer-maintained docs, key files, and other context captured after installation.
+
+If you want to seed knowledge from older work, add the important facts explicitly with `ctx_memory`, write a short project note in the repo, or keep working in the project and let the historian and dreamer promote recurring facts over time. Use `/ctx-recomp` when you need to rebuild Magic Context compartments from raw message history that Magic Context has captured in that session, such as after upgrading historian rules; it is not an importer for unrelated pre-install OpenCode or Pi sessions. The dashboard can also inspect the shared CortexKit database, memories, compartments, and dreamer runs without starting a coding session.
 
 <details>
 <summary><strong>Compatibility with other context-management plugins</strong></summary>