Spark wave 1: add Spark lane AGENTS.md

[8Dionysus]

Summary

• add the packaged Spark/AGENTS.md verbatim for wave 1
• keep root AGENTS.md authoritative and leave existing Spark/SWARM.md untouched
• verify Spark lane loading plus repo-native validation before merge

Validation

• python scripts/validate_stack.py

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Apply Spark policy by path, not task start location

The sentence here makes the Spark lane policy conditional on where a task was started, but AGENTS scoping is directory-based; this can cause Spark-specific constraints to be skipped when someone starts from repo root and then edits files under Spark/. That weakens the guardrails this file is meant to enforce, so the scope statement should describe coverage by file path (the Spark/ tree) rather than task origin.

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