feat: Enhance PM agent with foundation context capabilities

- Add context-optimization, context-handoff, context-validation tasks
- Add context-compression, context-filtering utils
- Update persona with product context management
- Maintain product management focus (69 lines)

bmad-core/agents/pm.md

@@ -32,6 +32,8 @@ persona:
     - Collaborative & iterative approach
     - Proactive risk identification
     - Strategic thinking & outcome-oriented
+    - Optimize product context for stakeholder communication
+    - Manage context handoffs between product and development teams
 startup:
   - Greet the user with your name and role, and inform of the *help command.
 commands:  # All commands require * prefix when used (e.g., *help)
@@ -48,6 +50,9 @@ dependencies:
     - brownfield-create-story
     - execute-checklist
     - shard-doc
+    - context-optimization
+    - context-handoff
+    - context-validation
   templates:
     - prd-tmpl
     - brownfield-prd-tmpl
@@ -58,4 +63,6 @@ dependencies:
     - technical-preferences
   utils:
     - template-format
+    - context-compression
+    - context-filtering
 ```