docs: update ssh-agent-setup cross-repo deps for new shell-system.sh layout (Sam and Hermes)

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Build: pass | Tests: FAIL — 1 failed

.agent/skills/ssh-agent-setup/SKILL.md

@@ -191,12 +191,14 @@ and retry. The root cause is remote.
 
 ## Cross-Repo Dependencies
 
-The ISO installer (`clawdie-iso/firstboot/shell-ssh.sh`) implements this
-skill automatically during first boot. After SSH key installation, function
-`clawdie_shell_ssh_seed_agent_config()` seeds:
+The ISO installer implements this skill across two firstboot modules:
 
-- `~/.profile` — agent launcher (Tier 1)
-- `~/.ssh/config` — `AddKeysToAgent yes`, `ForwardAgent no` (Tier 2)
-- `~/.tmux.conf` — base-index 1, mouse on (Tier 3, no update-environment)
+- `clawdie-iso/firstboot/shell-ssh.sh` — seeds `~/.ssh/config` with
+  `AddKeysToAgent yes` + `ForwardAgent no` after SSH key installation.
+- `clawdie-iso/firstboot/shell-system.sh` — generates `~/.profile`
+  (agent launcher) and `~/.bashrc` (sudo→mdo alias, ZFS snapshot safety,
+  agent fallback for non-login shells, PATH, prompt, aliases).
 
-All seeding is idempotent (grep-guarded against existing configs).
+`shell-system.sh` runs after `shell-ssh.sh` and owns the final dotfiles.
+The sudo→mdo decision is documented in `clawdie-iso/AGENTS.md` (System
+Configuration section).