[RFC #7748] feat(samples): standalone SQLite shared memory provider and concurrency suite

[RemanenetSpy (RemanenetSpy)]

Draft PR implementing the standalone SQLite shared memory provider sample requested in RFC #7748.

Changes Included:

• python/samples/agent_memory_sqlite/sqlite_shared_memory.py:
  • SQLiteSharedMemoryStore: Thread-safe SQLite store with WAL mode, foreign key enforcement, bi-temporal soft-invalidation (\�alid_from\ / \�alid_to), and optimistic atomic conditional replacement.
  • BoundSessionMemory: Context-bound tool wrapper instantiated by host orchestrator, binding caller credentials (\ enant_id, \scope_type, \scope_id, \�uthority_tier) server-side to prevent model-directed privilege escalation.
• python/samples/agent_memory_sqlite/test_sqlite_shared_memory.py:
  • 9 automated unit tests verifying scope isolation, authority tier overrides, atomic superseding, soft-delete tombstones, and trusted context binding.
  • Concurrency suite: 10 competing replacement workers with barrier synchronization (exactly 1 succeeds, 9 raise \ReplacementConflictError).
  • Harness repair test: Injected worker connection-setup failure cleanly aborts barrier, peer workers catch \ hreading.BrokenBarrierError, all threads join without hanging, and assertions strictly reject unexpected exceptions.
• python/samples/agent_memory_sqlite/README.md: Run instructions.

All 9 tests pass in ~0.5s:
\\�ash
pytest -v python/samples/agent_memory_sqlite/test_sqlite_shared_memory.py
\\

Resolves discussion in #7748.

[RemanenetSpy (RemanenetSpy)]

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