fix(review): 4 issues found in agent review of PR #535

BUG-1 (CRITICAL): messages.js line 522 — mismatched quote in
setComposerStatus('Reconnecting…') caused JS syntax error on the
reconnect path.

BUG-2 (HIGH): messages.js line 491 — broken template literal
'\\n\\n*{d.hint}*' restored to '\n\n*${d.hint}*'. Error hint
text was non-functional (missing $ prefix and escaped newlines).

BUG-3 (HIGH): messages.js — showApprovalCard(pending, pendingCount),
_approvalCurrentId, and approval_id in respondApproval() were removed,
regressing the simultaneous approval queue fix from PR #546. Restored
all three, including the '1 of N pending' counter and poll passthrough.

BUG-4 (LOW): api/streaming.py — MiniMax thinking delimiter regex
missing closing pipe: <|channel> -> <|channel|> in both
_strip_thinking_markup() and _looks_invalid_generated_title().

ALSO: test_issue487b.py docstring changed to raw string to fix
DeprecationWarning for invalid escape sequence '\s'.

tests/test_issue487b.py

@@ -1,4 +1,4 @@
-"""
+r"""
 Regression test for image src URL corruption by the autolink pass.
 
 Bug: the _al_stash before the autolink pass only stashed <a> tags.