chore(release/candidate): release 1.31.0

[Jacksunwei]

🤖 I have created a release beep boop

1.31.0 (2026-04-16)

Features

• Add "google-adk" user agent to Parameter Manager and Secret Manager clients (b8e8f6b)
• Add support for memories.ingest_events in VertexAiMemoryBankService (d69477f)
• Add Vertex AI Agent Engine Sandbox integration for computer use (7686848)
• Firestore support (1a9df8f)
• live: Add live_session_id to LlmResponse (bf84e2c)

Bug Fixes

• Bump minimum mcp version from 1.23.0 to 1.24.0 (494c360)
• cli: correct console URL path after adk deploy agent_engine (64ed1a6), closes #5336
• execute on_event_callback before append_event to persist plugin modifications (454188d), closes #3990
• make _EvalMetricResultWithInvocation.expected_invocation Optional for conversation_scenario support (#5215) (a4c9387)
• Pass in auth headers with header provider instead of connection params (e12b0af)
• populate required fields in FunctionDeclaration json_schema fallback (9b9faa4)
• Resolve BigQuery plugin issues with A2A transfers, spans, and metadata (9ca8c38)
• upgrade google-genai lower bound (8bc5728)

Code Refactoring

• live: Use send_client_content to send conversation history (67dc2eb)
• live: Use send_tool_response for function responses (70c5fc8)

Documentation

• update MCP Toolbox branding, binary version, and asset references (47fa7b7)

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