Bug: Heading with bold text produces malformed output

[tomoki-takahashi-oisix]

Description

When a heading contains bold text followed by additional content (e.g., a colon and text), the conversion produces malformed output.

Reproduction

from slackify_markdown import slackify_markdown

result = slackify_markdown('### **Step 1**: Description here')
print(repr(result))

Expected output

'*Step 1*: Description here\n'

Actual output

'**Step 1*: Description here*\n\n'

Additional test cases

slackify_markdown('### **Step 1**')        # => '**Step 1**\n\n' (bold not converted)
slackify_markdown('# **Test**: text')      # => '**Test*: text*\n\n' (malformed)
slackify_markdown('**Bold**')              # => '*Bold*\n' (works correctly)

Environment

• Python 3.12
• slackify-markdown 0.2.0