Cannot set up a proxy for a per-message profile whose name has special characters

[Kagamiin]

Describe the bug

When trying to set up a proxy for a PMP (using the /pmpproxy or pk;member commands), the command does not execute properly if the PMP's name contains any characters other than alphanumeric characters, spaces and underscores.

Additionally, the /pmpproxy command fails when the proxy pattern contains inline whitespace (this does not affect the equivalent pk;member command).

Reproduction

1. Enable PMPs in the experimental settings, then enable PK commands and proxying in the persona settings.
2. Set up a per-message profile whose name contains a special character other than _ (underscore), or a Unicode character; also set up one that doesn't contain such characters.
3. Attempt to set up a proxy for both PMPs via the /pmpproxy and/or pk;member commands, where the proxy string contains inline whitespace (e.g. (pxy) text).

Expected behavior

Both commands should execute properly, both in the case where the persona name contains a special character and where the proxy string contains whitespace.

Platform and versions

1. OS: Arch Linux (KDE Plasma 6.7.2/Wayland/nvidia-580xx, linux-zen 7.1.2)
2. Browser: Firefox 152.0.4
3. Sable version: v1.19.4 (d8938a6, app.sable.moe)
4. Matrix homeserver: chat.blahaj.zone

Additional context

This is very similar to #582, in which the command parsing regex is failing to take these edge cases into account.

This might be a good time to consider #341 and other general usability improvements to the PMP features?