fix(web): cap the approval takeover at the composer's text height

The approval panel replaces the InputBar while a sandbox escalation waits,
and its justification and command are unbounded model text. With no height
cap, a long command grew the card until the refuse/allow row went under the
fold: at 900x700 the action row's bottom landed at y=749, so the user could
read the request and not answer it.

Justification and command now scroll in one region capped at the same height
as the composer's draft area, with the amber strip and the action row outside
it. The cap is one value with two consumers — declared as
--dsh-composer-text-max-height on ConversationRoot's .composerSeat, the
composer chain's only shared ancestor — so the seat cannot cap its two states
differently. The card rebinds the l2 scrollbar pair like every other scrolling
surface on an elevated background.

Covered by a new web e2e scenario that drives the real composition (read-only
session, denied write, the model's escalation retry, answer clicked through
the panel) and measures the live panel at two viewport heights against the
composer's own cap, read off the textarea rather than hardcoded.

.agents/notes/implemented/bug-fix/2026-07-30-approval-panel-command-cap.i18n.yaml

@@ -0,0 +1,6 @@
+# Bilingual-pair consistency record (docs/i18n/README.md): the git blob hash of each
+# side as of the last confirmed-consistent state. Both languages carry equal authority;
+# after editing either side, bring the other along and re-record with:
+#   pnpm run verify-translation-pairing --write .agents/notes/implemented/bug-fix/2026-07-30-approval-panel-command-cap.md
+2026-07-30-approval-panel-command-cap.md: a9282f132e655833cfe687409c287c5afd538d50
+2026-07-30-approval-panel-command-cap.zh.md: 7eb40942e10134d43478e53e06c584bb97d3bb8f