feat: add Agent Episodic Memory support (recall node)

[mjnovice]

Summary

• Memory recall graph node: When MemoryConfig is passed to create_agent(), a MEMORY_RECALL node is inserted before INIT that queries the UiPath Memory service and stores the systemPromptInjection in graph state. The INIT node reads it and appends to the system prompt.
• New types: MemoryConfig, AgentGraphNode.MEMORY_RECALL, InnerAgentGraphState.memory_injection
• Dependency: bumps uipath-platform >= 0.1.31 for MemoryService types (depends on feat: scaffold MemoryService for Agent Episodic Memory (URT migration) uipath-python#1467)

Note: Escalation memory is not included in this PR. Only episodic memory recall is being changed.

Graph with memory enabled

START → MEMORY_RECALL → INIT → AGENT ↔ TOOLS → TERMINATE → END

Files changed

• types.py — MemoryConfig dataclass, memory_injection field on inner state, MEMORY_RECALL node enum
• memory_node.py — New: memory recall graph node
• agent.py — create_agent() accepts optional memory parameter
• init_node.py — Reads memory_injection from state and appends to system prompt
• __init__.py — Exports MemoryConfig

Relationship with UiPath/uipath-agents-python#374

This PR and UiPath/uipath-agents-python#374 together implement the full Agent Episodic Memory feature across both repos:

Concern	This PR (uipath-langchain-python)	UiPath/uipath-agents-python#374
Memory recall graph node	Implements MEMORY_RECALL node, MemoryConfig, and INIT-node injection	Resolves MemoryConfig from agent definition (isAgentMemoryEnabled + memorySpaceId) and passes it to create_agent()
Memory module	memory_node.py — builds MemorySearchRequest, calls sdk.memory.search_async()	memory.py — contains build_memory_search_request() and retrieve_memory_injection() helpers (to be replaced by the graph node from this PR)
Factory wiring	Exposes MemoryConfig for callers to pass	_get_memory_config() extracts memory settings from AgentDefinition and constructs MemoryConfig

Merge order: This PR should merge first (or concurrently with UiPath/uipath-python#1467). Then UiPath/uipath-agents-python#374 can be updated to:

1. Remove the runtime-level _populate_memory_context() mutable-dict approach
2. Instead, pass MemoryConfig to create_agent(memory=...) in graph.py
3. Remove memory_context threading through the message factory

Both PRs depend on UiPath/uipath-python#1467 (uipath-platform >= 0.1.31) for the MemoryService types.

Test plan

• 20 new unit tests (memory node, escalation cache, escalation ingest)
• Existing test_create_agent.py tests pass (graph structure unchanged when memory=None)
• Full suite: 1544 passed (2 pre-existing failures from missing optional deps)
• E2E test with real memory space (requires feat: scaffold MemoryService for Agent Episodic Memory (URT migration) uipath-python#1467 merged)

E2E flow tested with https://github.com/UiPath/Agents/pull/5082/changes enabled

Ingestion

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