agentic-memory integration suite: per-test schema isolation so parallel runs pass #100

What to build

cargo test -p agentic-memory --test integration -- --ignored passes at default test parallelism against the single pg.yml fixture database. Today the 17 tests share tables and interfere: 5–7 varying failures per parallel run, all green only with --test-threads=1 (OpenWolf bug-125; observed while landing #43 / PR #98).

The repo already has the right pattern in-tree: agenticd's reverse-migration integration tests give each test its own temp schema via search_path, so they run in parallel safely. Apply the same isolation to the agentic-memory suite. Watch for shared cluster-level resources the schema trick doesn't cover (replication slots, advisory lock keys) — those may need per-test naming too.

Acceptance criteria

• Three consecutive cargo test -p agentic-memory --test integration -- --ignored runs pass at default parallelism
• No test semantics weakened (same assertions; no new #[ignore], no serialization workaround)
• --test-threads=1 still passes (no new ordering assumptions)

Blocked by

None — can start immediately.