chore: ignore generated notebook toml artifacts

[Mjboothaus]

Summary

• add ignore rules for generated notebook TOML artifacts under examples/notebooks/
• keep repository status clean after notebook conversion and exploratory runs
• leave source notebooks and runtime code untouched

Validation

• git check-ignore -v examples/notebooks/black_scholes_blueprint.toml
• git check-ignore -v examples/notebooks/black_scholes_pricing.toml
• git check-ignore -v examples/notebooks/spec_black_scholes.runtime.toml
• git check-ignore -v examples/notebooks/spec_black_scholes.toml

Context

• Conversation: https://app.warp.dev/conversation/79aa7721-1947-44e5-840f-d20883bd8624

Co-Authored-By: Oz oz-agent@warp.dev

[semanticdiff-com]

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