feat: Add agent long-term memory with ondemand and always store modes

[vinodvx]

Description

• Adds long-term memory to the agent SDK via agent.WithMemory, with recall before each run and store after (ondemand via save_memory or always via run-end extract).
• Supports inmem, Weaviate, and pgvector backends with scoped recall/store in local and Temporal runtimes.
• Wires memory into eval-harness and benchmarks through the existing YAML config (no extra files), plus an examples/agent_with_memory example.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• Refactor / chore

Related issues

Closes #22

Checklist

• [*] I have run make check
• [*] I have run task examples:all
• [*] I have run make tidy if I added or removed dependencies
• [*] Commit messages follow conventional commits (e.g. feat:, fix:, docs:)
• [*] I have added/updated tests for my changes
• [*] Documentation is updated if needed

[codecov]

Codecov Report

❌ Patch coverage is 59.71538% with 736 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
internal/testing/inmem_memory.go	0.00%	120 Missing ⚠️
pkg/memory/weaviate/memory.go	68.82%	84 Missing and 27 partials ⚠️
pkg/memory/pgvector/memory.go	77.97%	54 Missing and 22 partials ⚠️
internal/runtime/temporal/agent_workflow.go	21.87%	46 Missing and 4 partials ⚠️
internal/runtime/base/runtime.go	65.60%	36 Missing and 7 partials ⚠️
eval-harness/runner/setup/config.go	17.02%	39 Missing ⚠️
internal/runtime/base/memory.go	85.04%	25 Missing and 10 partials ⚠️
benchmarks/setup/config.go	0.00%	34 Missing ⚠️
eval-harness/runner/setup/mock_llm.go	0.00%	22 Missing ⚠️
pkg/agent/config.go	54.16%	18 Missing and 4 partials ⚠️
... and 19 more

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