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/hooks-config.ts

@@ -1601,7 +1601,7 @@ export function agentSkillDirFor(casePath: string, dir: AgentSkillDir): string {
  * Add or remove the Codeman agent skill in `<case>/<dir>/codeman`, where `dir` is the
  * skills directory the session's CLI scans (default: Claude Code's `.claude/skills`;
  * callers resolve it with `agentSkillDir()`), mirroring `applyStatusLineConfig`'s
- * shape. Gated by the synced `agentSkillEnabled` app setting (default OFF).
+ * shape. Gated by the synced `agentSkillEnabled` app setting (default ON: an absent key is ON).
  *
  * Call-site policy is ADD-ONLY on session create (callers pass `enabled: true` or
  * skip the call), for the statusLine reason: sessions in a repo share one workspace,