docs: trim firstmate agent guidance duplication

.agents/skills/harness-adapters/SKILL.md

@@ -18,7 +18,8 @@ The captain may override that file at session start or later; a per-task instruc
 Secondmates have their own harness knob, so a secondmate can run on a different adapter than crewmates.
 `config/secondmate-harness` is the harness the primary uses to launch SECONDMATE agents, resolved through the fallback chain `config/secondmate-harness` -> `config/crew-harness` -> firstmate's own.
 An absent or `default` `config/secondmate-harness` therefore behaves exactly as the crew harness did before this knob existed (secondmates launched on the crew harness); setting it splits the two.
-`config/crew-dispatch.json` and `config/crew-harness` are inherited by secondmate homes (the primary pushes them down so a secondmate's own crewmates use the primary's dispatch profiles and static harness value), while `config/secondmate-harness` is the primary's own setting and is never inherited - secondmates do not spawn secondmates.
+`config/crew-dispatch.json`, `config/crew-harness`, and `config/backlog-backend` are inherited by secondmate homes.
+This skill owns only the harness-relevant consequence: a secondmate's own crewmates use the primary's dispatch profiles and static harness value, while `config/secondmate-harness` is the primary's own setting and is never inherited - secondmates do not spawn secondmates.
 Inheritance copies the literal `config/crew-harness` file, so for a secondmate's own crewmates to run on the primary's crewmate harness the captain must set `config/crew-harness` to a concrete adapter name, such as `codex`.
 If `config/crew-harness` is unset or `default`, there is no concrete value to inherit, so the secondmate's own crewmates fall back to the secondmate's own/detected harness rather than the primary's effective crewmate harness.
 Inheritance also copies the literal `config/crew-dispatch.json` file, so secondmates apply the same best-fit profile rules for their own crewmates.