doc: generate llms.txt #7291

Job	Run time
Build slim tarball	1m 11s
aarch64-linux: Cache V8 build	21s
x86_64-linux: with shared libraries	27m 16s
x86_64-darwin: with shared libraries	37m 53s
aarch64-darwin: with shared libraries	22m 42s
aarch64-linux: with shared openssl-1.1.1w	23m 53s
aarch64-linux: with shared boringssl-0.20260508.0	24m 3s
aarch64-linux: with shared openssl-3.6.2	25m 18s
aarch64-linux: with shared openssl-3.5.6	24m 31s
aarch64-linux: with shared openssl-4.0.0	25m 20s
aarch64-linux: with shared openssl-3.0.20	25m 28s
	3h 57m 56s

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