fix(readmymind): style the modal footer, point the empty-result copy at the steer note

The footer buttons shipped with class="btn btn-secondary/primary", but no
.btn or .btn-secondary rule exists in this codebase, so all four rendered
as unstyled UA buttons. Moved them to the btn-toolbar convention every
other modal footer uses, with a scoped flex-row footer rule (btn-toolbar
is display:flex, block-level) mirroring the runSummaryModal footer.

Send's accent needs a (0,4,0) re-assert: the skin block's bare
.btn-toolbar rule is (0,2,1) under html:not([data-skin="og"]) and beats
.btn-toolbar.btn-primary (0,2,0), the same specificity trap CLAUDE.md
documents for mobile.css. Scoped to this modal; the repo-wide greying of
btn-primary on non-OG skins is pre-existing and left as a design call.

The empty-result copy now points at the steer note sitting right below
it ("Add a steer note and Rethink to try again"), zh-CN updated.

Verified with the steer E2E (still green) plus desktop, phone (390px),
and error-phase screenshots; static guards extended to pin the footer
convention and the accent re-assert.

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

src/web/public/i18n.js

@@ -255,7 +255,8 @@
     'Read My Mind: predict your next prompt': '读心术：预测您的下一条提示',
     'Predict my next prompt': '预测我的下一条提示',
     'Reading your mind…': '正在读取您的想法…',
-    'No suggestion this time. Rethink to try again.': '这次没有建议。点击「重想」再试一次。',
+    'No suggestion this time. Add a steer note and Rethink to try again.':
+      '这次没有建议。可添加引导备注后点击「重想」再试一次。',
     Rethink: '重想',
     Insert: '插入',
     "Put the text on the session's composer without submitting it": '将文本放入会话输入框但不提交',