feat: integrate Graphiti knowledge graph for agent memory

[cyrusagent]

Summary

• Add Graphiti MCP server integration for persistent team memory, gated behind GRAPHITI_MCP_URL env var
• Agents recall relevant context at session start via search_memory_facts and store learnings post-session via add_memory
• Zero behavior change when env var is not set

Changes

• EdgeWorker.ts — Add conditional Graphiti MCP server to buildMcpConfig() (same pattern as Slack)
• RunnerSelectionService.ts — Add mcp__graphiti to workspace MCP tool allowlist
• PromptBuilder.ts — Add formatMemoryContext() for recall instructions in <memory_context> block; skip memory-reflection subroutine when Graphiti not configured
• registry.ts — Add memoryReflection subroutine definition; append to full-development and debugger-full procedures
• memory-reflection.md — New subroutine prompt for post-session learning capture (0-5 facts per session)

Test plan

• Set GRAPHITI_MCP_URL=http://localhost:8000/mcp/ and run docker compose up with Graphiti container
• Trigger a full-development session — verify agent calls search_memory_facts at start
• Verify memory-reflection subroutine runs after concise-summary and stores learnings via add_memory
• Unset GRAPHITI_MCP_URL — verify no Graphiti references in prompts or MCP config
• Verify memory-reflection auto-skips when Graphiti is not configured

Resolves CYPACK-1001