History of tiers 4 changes

In crates/flow/src/runner.rs, lines 532–553 on cedd12342afac41162c56d51b436c8260d763a4a492f11a8bad6efa04094f25d. Every change that wrote or deleted one of these lines, or deleted a line from between them. Exact, because each line keeps its identity across edits; edits elsewhere in the file are not here. Also: oxy log -L 532,553:crates/flow/src/runner.rs.