Parse `/tree/...` URLs by first capturing the full branch candidate, then
iteratively resolving valid branch names for GitHub API lookups and deriving
the remaining path as base directory. Also adjust env var editor/input view
classes (`font-sans`, `w-full`) and add/extend feature tests for both branch
parsing and multiline toggle rendering.
Add `monospace` prop to Textarea component so font-mono is no longer
applied by default. Apply it explicitly to env variable editors, private
key fields, and shared variable forms where monospace is appropriate.
Use Alpine.js x-data/x-model to make the multiline toggle reactive
without a full Livewire round-trip. Add wire:key on the input/textarea
wrappers to force proper DOM replacement when switching modes.
