test(report): strengthen assertion in test_tool_call_count_shown_when_present

[decko]

Summary

Strengthens the weak assertion in test_tool_call_count_shown_when_present in tests/test_report_html.py.

Before (weak):

assert "5 tool calls" in content            # could match anywhere in the document
assert 'class="tool-call-count"' in content  # could match the CSS definition block

These two separate checks could each pass independently in the wrong places — e.g., the class name appears in the <style> block (as .tool-call-count { ... }), and the count text could appear in a comment or other element.

After (strong):

assert '<span class="tool-call-count">5 tool calls</span>' in content

This single atomic assertion verifies both the count value and the CSS class appear together in the correct HTML element, exactly matching the Jinja2 template output. This eliminates false positives from independent substring matches.

Acceptance Criteria

• The weak two-part assertion is replaced with a single atomic HTML element check
• The new assertion matches the actual Jinja2 template output
• All existing tests continue to pass (1845 tests, 4 skipped)
• No regressions introduced

Review Results

Specialist	Verdict	Findings
Implementation	✅ PASS	0 issues
Verification	✅ PASS	All 1845 tests pass, lint clean
Review	✅ pass	0 findings

Refs #274

Assisted-by: Claude Opus 4.6 (1M context) noreply@anthropic.com
Assigned-by: decko