README: give copy-paste commands for opening/copying the SSH pub key; note hotspot works

The '~/.ssh/id_ed25519.pub' path meant nothing to someone unfamiliar with the
terminal or filesystem — they had no way to actually get to that file. Add
per-OS one-liners to either open it in the default text editor or copy its
contents straight to the clipboard, so there's no need to navigate anywhere.
Also note in the 'Use it' step that a phone hotspot works (transfer stays
local, no carrier data used) but a real router is faster/more stable for big
drives.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Author: sourylime

README.md

@@ -102,9 +102,23 @@ The comma only allows computers whose SSH key is registered to it via a GitHub a
    - **macOS / Linux:** `~/.ssh/id_ed25519.pub`
    - **Windows:** `%USERPROFILE%\.ssh\id_ed25519.pub` (typically
      `C:\Users\<your username>\.ssh\id_ed25519.pub`)
-2. **Add the `.pub` key to a GitHub account.** Open the `.pub` file in any text editor
-   (Notepad, TextEdit, etc.) and copy its entire contents — it's one long line starting
-   with `ssh-ed25519`. Go to
+
+   That `~` is just shorthand for your home folder, not a real folder to browse to —
+   the easiest way to get the key is straight from the terminal. **To open it** in
+   your OS's default text editor, paste one of these into the same terminal window and
+   press Return:
+   - **macOS:** `open -e ~/.ssh/id_ed25519.pub`
+   - **Linux:** `xdg-open ~/.ssh/id_ed25519.pub`
+   - **Windows (PowerShell):** `notepad $env:USERPROFILE\.ssh\id_ed25519.pub`
+
+   Or **skip opening it entirely** and copy the key straight to your clipboard:
+   - **macOS:** `pbcopy < ~/.ssh/id_ed25519.pub`
+   - **Linux:** `xclip -sel clip < ~/.ssh/id_ed25519.pub` (if that command isn't found,
+     install it first: `sudo apt install xclip`, then run it again)
+   - **Windows (PowerShell):** `Get-Content $env:USERPROFILE\.ssh\id_ed25519.pub | Set-Clipboard`
+2. **Add the `.pub` key to a GitHub account.** If you copied it to the clipboard above,
+   just paste it. Otherwise, in the text editor that opened, select all and copy — it's
+   one long line starting with `ssh-ed25519`. Go to
    [github.com/settings/keys](https://github.com/settings/keys) → **New SSH key**,
    paste it in, and save. (Don't have a GitHub account? Making one is free at
    [github.com](https://github.com).)
@@ -118,6 +132,11 @@ The comma only allows computers whose SSH key is registered to it via a GitHub a
    drive and its size.
 3. Tick the ones you want (or **Download All**) and watch them transfer. Done!
 
+> A **phone hotspot** works fine for this — the transfer stays local between the comma and
+> your computer, so it doesn't use any of your carrier data. A proper **WiFi router** is
+> still the better choice when you have one, since it's generally faster and more stable
+> for long or large drives.
+
 ---
 
 # Advanced (environment variables)