[feature] A delay on startup before fetching / soft start feature? limit of processing when load average too high?

When a computer comes out of sleep mode, many local network connections are not yet ready etc

Some kind of soft-start mechanism that is enabled as an env var

- no fetching for atleast `X` seconds
- then "ramp up" seconds to allow all the fetch workers to wake up slowly (so for example if you have 10 workers and ramp up is set to 60 seconds, then one every 6 seconds would come to life)

No file, test, or entry point is named. Start by locating the startup and fetch-worker scheduling paths, then clarify the environment-variable interface and how sleep recovery and high load average should affect fetching. Done means the behavior and configuration are defined, implemented, and covered by tests for the initial delay and gradual worker ramp-up.

Written by the indexing model from the issue text.