Refactor knowledge.md into AGENTS.md + docs/ #5991

Job	Run time
build-and-check	3m 2s
test-integration-packages/billing	1m 10s
test-integration-packages/agent-runtime	43s
test-integration-packages/internal	1m 9s
test-integration-sdk	1m 28s
test-web	56s
test-cli	55s
test-integration-web	48s
test-integration-common	46s
test-common	50s
test-packages/agent-runtime	50s
test-integration-cli	42s
test-.agents	51s
test-packages/billing	43s
test-packages/internal	52s
test-sdk	46s
	16m 31s

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