Add copy commands to Query Store context menu (#91)

[erikdarlingdata]

Summary

• Right-click context menu on Query Store grid now includes copy commands for all identifier and data columns
• Copy Query ID, Plan ID, Query Hash, Plan Hash, Module Name, Query Text, and full Row (tab-delimited)
• Items are disabled when no row is selected or the value is empty

Test plan

• Right-click shows all copy menu items
• Copy Query ID/Plan ID copies numeric value
• Copy Query Hash/Plan Hash copies hex string
• Copy Module Name disabled for ad-hoc queries
• Copy Query Text copies full SQL
• Copy Row copies all columns tab-delimited
• Load Plan still works

Closes #91

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