Missing-dependency panel prints an uncopyable install command: over-escaped closing bracket

[leesaenz]

What happens

The DependencyMissingError panel prints an install command that cannot be
copied and run. Running phantom separate without the extra installed:

╭───────────────────────────── Missing Dependency ─────────────────────────────╮
│ phantom-audio-separation is not installed.                                   │
│                                                                              │
│ Install with: uv tool install "phantom-audio[separation\]" --python 3.13     │
╰──────────────────────────────────────────────────────────────────────────────╯

Note the stray backslash before the closing bracket: [separation\].

Cause

src/phantom/cli/_formatting.py:234:

f'Install with: [green]uv tool install "phantom-audio\\[{exc.extra}\\]" --python {RECOMMENDED_PYTHON}[/green]'

Rich markup only treats [ as a tag opener, so \[ is the documented escape for
a literal opening bracket and renders correctly. ] is not special and has no
escape sequence — Rich passes \] through unchanged, so the backslash reaches
the terminal.

The opening bracket is escaped correctly; the closing one is over-escaped.

Fix

-f'Install with: [green]uv tool install "phantom-audio\\[{exc.extra}\\]" --python {RECOMMENDED_PYTHON}[/green]'
+f'Install with: [green]uv tool install "phantom-audio\\[{exc.extra}]" --python {RECOMMENDED_PYTHON}[/green]'

Impact

Cosmetic, but it lands in front of a user who is already blocked and reaching for
the copy button. In zsh the pasted command fails outright:

$ uv tool install "phantom-audio[separation\]" --python 3.13
error: Expected an alphanumeric character while parsing extra name

Notes

render.py:111 and render.py:226 also raise DependencyMissingError panels
through the same renderer, so every missing-extra message carries the same stray
backslash — not just separate.

A test asserting the rendered panel text contains [separation] and not
[separation\] would catch it. Asserting on the markup string rather than the
rendered output would not, since the bug is in how Rich interprets the escape.