doc: generate llms.txt #7304

Job	Run time
Build slim tarball	1m 28s
aarch64-linux: Cache V8 build	22s
x86_64-linux: with shared libraries	26m 48s
x86_64-darwin: with shared libraries	51m 0s
aarch64-darwin: with shared libraries	24m 32s
aarch64-linux: with shared openssl-3.0.20	22m 42s
aarch64-linux: with shared openssl-1.1.1w	24m 21s
aarch64-linux: with shared openssl-3.6.2	24m 26s
aarch64-linux: with shared boringssl-0.20260508.0	24m 10s
aarch64-linux: with shared openssl-3.5.6	24m 21s
aarch64-linux: with shared openssl-4.0.0	23m 21s
	4h 7m 31s

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