Development record

`35-drain.md:942` lists the cap refusals and line 12 says the cap bounds the lanes a drain opens, but the chapter never says that `abcd drain --max 0` is accepted and opens every lane. The run prints `cap: none (--max not given: all)` although the flag was given, and writes `"max": 0`. The refusal of `--max -1` at `internal/core/implement/loop/drain.go:369` asks for a whole number of lanes, 1 or more, which excludes the 0 it accepts, and `abcd build next` refuses `--max 0` (`internal/surface/cli/build.go:430`).