docs: pdp proof clock docs #2381

Job	Run time
ci-lint	14s
gen-check	6m 25s
setup-params	7s
build-calibnet	5m 14s
build-2k	4m 50s
build-forest	4m 54s
build-debug	5m 16s
build-mainnet	5m 1s
lint	3m 56s
gofmt	23s
mod-tidy-check	39s
test (test-all, `go list ./... \| grep -v curio/itests`)	4m 27s
test (test-itest-alertnow, ./itests/alertnow_test.go)	2m 29s
test (test-itest-curio, ./itests/curio_test.go)	5m 4s
test (test-itest-harmonyDB, ./itests/harmonydb_test.go)	4m 45s
	53m 44s

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