feat(settings): the codeman agent skill is on by default

agentSkillEnabled now reads an absent key as ON, the way
workspaceHooksEnabled does: only an explicit false turns it off. A new
session therefore finds the codeman skill in its folder without a
setting first, and with it the verbs that hand work to other CLIs and to
the local model on this Mac. Settings shows the switch on for the same
absent key.

The injection itself is unchanged: add-only, marker-owned, never through
a symlink, never for remote sessions or a plain shell. Turning the
setting off still removes nothing already written.

The quick-start test now pins the new default (injected on an absent
key, nothing after an explicit false), and the docs that said "default
off" say when that changed.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/config/cli-registry/types.ts

@@ -633,7 +633,7 @@ export interface CliCapabilities {
   /**
    * Codeman may write its agent skill (`skills/codeman`) into this CLI's workspace and
    * seed its per-session preamble (behind the synced `agentSkillEnabled` setting,
-   * add-only, marker-owned). Where it lands comes from `agentSkillDir` below.
+   * default ON, add-only, marker-owned). Where it lands comes from `agentSkillDir` below.
    */
   agentSkillInjection: boolean;
   /**