Refactor knowledge.md into AGENTS.md + docs/ #5986

Job	Run time
build-and-check	3m 6s
test-integration-packages/internal	1m 6s
test-integration-sdk	1m 27s
test-integration-common	42s
test-integration-web	49s
test-integration-cli	42s
test-integration-packages/agent-runtime	45s
test-packages/agent-runtime	52s
test-common	39s
test-sdk	46s
test-web	48s
test-integration-packages/billing	1m 8s
test-.agents	44s
test-cli	1m 0s
test-packages/billing	48s
test-packages/internal	1m 10s
	16m 32s

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