Add a 26.6 agent-memory lifecycle walkthrough

[Kseniase]

Add a 26.6 agent-memory lifecycle walkthrough

What changed

• Adds notebooks/agent_memory/short_term_vs_long_term_agent_memory_26_6.ipynb.
• Demonstrates short-term thread state, summaries, typed durable memory, metadata and thread scoping, context cards, updates, TTL, and deletion.
• Uses the Oracle AI Agent Memory 26.6 API baseline, including MemoryExtractionConfig, memory_store_id, metadata filters, background extraction, update APIs, TTL, and context-card type minimums.
• Includes observable assertions for exact-thread versus cross-thread retrieval and for message versus durable-memory deletion.
• Adds a README entry for the new notebook.

Why

The companion notebook supports the Oracle Developers article Short-Term vs Long-Term Agent Memory with Oracle AI Agent Memory 26.6. It turns the conceptual distinction into a complete memory lifecycle that developers can inspect and rerun.

Developer impact

Readers can use one compact example to understand:

• what stays in the active thread;
• what becomes durable memory;
• how deterministic scope is applied before relevance ranking;
• how context cards differ from summaries;
• how corrections, TTL, and deletion affect stored memory.

Validation

• Notebook JSON validated with nbformat.
• Every Python cell was syntax-compiled with top-level await support.
• All 17 code cells executed successfully on July 15, 2026, against Oracle AI Database 26ai Free 23.26.2.0.0 on ARM64 with oracleagentmemory==26.6.0 and Python 3.12.4.
• Runtime validation used gpt-5.4 and text-embedding-3-small; all lifecycle assertions passed with no notebook errors or warnings.
• Repository formatting and notebook checks passed.

OCA

The Oracle Contributor Agreement was completed under the GitHub identity used for this pull request. The GitHub OCA check should be confirmed before the PR is marked ready for review.

[oracle-contributor-agreement]

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• PR author: Kseniase
• kseniase@gmail.com (@Kseniase)

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[Kseniase]

I completed the Individual Oracle Contributor Agreement on July 15, 2026, with GitHub username Kseniase, matching this PR. The latest OCA check is still failing after the signed agreement completed. Could a maintainer please recheck once Oracle’s acknowledgment has been processed?