fix(harvest): pass embedder to extract_and_store_knowledge (fixes #453)

[mickume]

Summary

• Pass embedder=self._embedder to extract_and_store_knowledge() in _harvest_knowledge(), fixing the broken embedding pipeline for session-extracted facts.
• The EmbeddingGenerator was already created and stored on the runner — it just wasn't forwarded to the harvest call.
• Add regression test to verify the wiring.

Closes #453

Changes

File	Change
agent_fox/engine/session_lifecycle.py	Pass embedder=self._embedder to extract_and_store_knowledge()
tests/unit/cli/test_knowledge_wiring.py	Add test_embedder_passed_to_extract regression test

Tests

• test_embedder_passed_to_extract: verifies the embedder instance is forwarded from the runner to the harvest function

Verification

• All existing tests pass: ✅ (4943 passed)
• New test passes: ✅
• Linter / formatter: ✅
• No regressions: ✅

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