Clarify live include is default; pin is exception for derived slots

Align proposal with coulomb spreadsheet-like live resolve policy.

docs/proposed-stale-derived-and-include-pinning.md

@@ -38,8 +38,12 @@ explicitly.
 ## Non-goals (v1)
 
 - Full workflow UI inside markitect-tool.
-- Automatic background regeneration as default policy.
-- Replacing live `mkt:include` (live resolve remains valid).
+- Automatic background regeneration of **pinned** snapshots without user consent.
+- Replacing live `mkt:include` as the default (live resolve remains the **default** product mode — spreadsheet-like).
+
+**Product policy (coulomb):** live includes by default; pin is the exception  
+(“paste values”). Stale → alternative → replace|keep applies to **pinned**  
+derived slots and to projection fields, not to pure live resolve.
 
 ## Proposed document syntax