feat: Enhance Slack import and memory promotion rules to better capture multi-channel, multi-year contributions and improve user role identification

knowledge/memory-promotion-rules.md

@@ -75,6 +75,8 @@ Use these files when:
 - a person's identity matters repeatedly
 - a role becomes associated with a specific person
 - a stakeholder's communication or approval patterns affect future work
+- a human appears across multiple channels or years with repeated technical, process, or approval signal
+- the archive makes the collaboration pattern clear even if the formal title is still unknown
 
 Prefer:
 
@@ -82,6 +84,8 @@ Prefer:
 - `index.md` for active roster
 - one file per person for person-specific context
 
+If exact role confidence is low, store the person's repeated project relationship instead of inventing a title.
+
 ---
 
 ## Do Not Promote