fix: add --batch flag to GPG command to prevent /dev/tty error (#69)

* fix: add --batch flag to GPG command to prevent /dev/tty error

The GPG command in the Linux installation step was attempting to access
/dev/tty in non-interactive GitHub Actions environments, causing failures
when the action was used multiple times in a workflow.

Adding the --batch flag tells GPG to run in non-interactive mode and
prevents it from trying to access /dev/tty.

Fixes #68

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

* chore: add --yes and --no-tty flags for maximum compatibility

Per review feedback, adding --yes and --no-tty flags in addition to --batch
provides more defensive protection against any TTY access attempts by GPG:

- --batch: prevents interactive prompts
- --yes: auto-accepts any questions
- --no-tty: ensures GPG never uses TTY even for warnings

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: ekampf

action.yml

@@ -148,7 +148,7 @@ runs:
       shell: bash
       run: |
         # Import Twingate GPG key for signature verification
-        curl -fsSL https://packages.twingate.com/apt/gpg.key | sudo gpg --dearmor -o /usr/share/keyrings/twingate-client-keyring.gpg
+        curl -fsSL https://packages.twingate.com/apt/gpg.key | sudo gpg --batch --yes --no-tty --dearmor -o /usr/share/keyrings/twingate-client-keyring.gpg
 
         # Add Twingate repository with GPG key verification
         echo "deb [signed-by=/usr/share/keyrings/twingate-client-keyring.gpg] https://packages.twingate.com/apt/ * *" | sudo tee /etc/apt/sources.list.d/twingate.list