Fix single newlines not collapsed in commands panel in rich mode

[JSap0914]

Bug

In _make_command_help (used to render each command's help text in the Commands panel), the condition guarding newline collapsing was inverted:

# Before (buggy)
if markup_mode != MARKUP_MODE_RICH and not paragraphs[0].startswith("\b"):

This meant:

• rich mode (the default): single newlines within a subcommand's first help paragraph were not collapsed → the Commands panel showed each line on its own table row.
• markdown mode: single newlines were collapsed unnecessarily (Markdown renders them as spaces anyway).

Every other function in the file uses markup_mode != MARKUP_MODE_MARKDOWN for the same guard (_get_help_text, _get_parameter_help).

Reproducer

import typer
from typer.testing import CliRunner

app = typer.Typer(rich_markup_mode="rich")

@app.command()
def cmd1():
    """First line
    second line"""

@app.command()
def cmd2():
    """Normal help"""

result = CliRunner().invoke(app, ["--help"])
print(result.output)

Before fix – Commands panel:

╭─ Commands ─────────────────────╮
│ cmd1  First line               │
│       second line              │  ← broken: extra row
│ cmd2  Normal help              │
╰────────────────────────────────╯

After fix:

╭─ Commands ─────────────────────╮
│ cmd1  First line second line   │  ← correct: collapsed
│ cmd2  Normal help              │
╰────────────────────────────────╯

Fix

Change the one condition in _make_command_help:

# After (fix)
if markup_mode != MARKUP_MODE_MARKDOWN and not paragraphs[0].startswith("\b"):

Verification

pytest tests/test_rich_markup_mode.py::test_commands_panel_single_newline_collapsed -v

Result: 2 passed (rich mode and markdown mode both collapse correctly).

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