feat(issue-24): startup dialogs come from the agent adapter and are handled while waiting for the TUI

handle_startup_dialogs was a claude-only string ladder called only when
AGENT=claude, and wait_for_tui_ready does not treat a dialog screen as ready.
So agy, grok and codex sat on their directory-trust prompt for the full
readiness timeout, the session was recorded as tui-ready-timeout, and
onboarding injection was disabled (create_session.sh:313-314) - a human had to
accept each dialog by hand.

The signatures and accept keys move to the adapters as `startup_dialogs`
(pattern, keys, kind), published through the existing `facts` eval contract as
MAM_STARTUP_DIALOGS. claude's ladder moves over verbatim; agy takes Enter, grok
y, codex Enter, and codex's update notice takes 2 (Skip), which blocks a start
just as hard while changing nothing. kind is `trust` or `notice`:
--no-auto-trust leaves trust dialogs to a human and still answers notices,
since trusting a directory makes codex load its project-local config, hooks and
exec policy.

Re-sending is gated by time (MAM_DIALOG_RESEND_S, default 5s), not by frames.
#24's comment reports that `--source visible` keeps showing an accepted dialog
for a while, and _pane_capture hardcodes that source, so "still on screen" is
not evidence the keys were missed; acceptance is judged by the ready tokens
alone.

Two existing tests asserted the old shape and are updated, not weakened:
b19's "Escape branch stays" now looks for it in claude's adapter, and c1b's
"Enter once per iteration" becomes "never twice for one frame", which the
cooldown satisfies strictly more tightly.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

.agents/skills/lib_py/agents/base.py

@@ -156,6 +156,21 @@ class BaseAgentAdapter:
     def modal_tokens(self) -> Optional[str]:
         return None
 
+    @property
+    def startup_dialogs(self) -> List[tuple]:
+        """Blocking modals this CLI can show before its TUI is usable, most
+        specific first: (pattern, keys, kind).
+
+        `pattern` is an extended-regex signature matched against the pane tail,
+        `keys` are herdr send-keys arguments sent in order, and `kind` is
+        'trust' (a directory-trust prompt, gated by --auto-trust) or 'notice'
+        (anything else that blocks the start, always answered).
+
+        Issue #24: without this the start-up trust prompts of agy, grok and
+        codex burn the whole readiness timeout and onboarding is skipped.
+        """
+        return []
+
     @property
     def strong_ready_tokens(self) -> str:
         return self.ready_tokens