fix: remove allowedTools restriction blocking review posting

[toolpathguy]

Relates to #5

Problem

The --allowedTools flag in the SDK context acts as a tool registry — it restricts which tools the agent can see at all. Our allowlist only included file-reading tools, which blocked Claude from using the GitHub tools the action injects for posting PR reviews and comments. This caused 13 permission denials per run and max-turns exhaustion ($1+ wasted each time).

Fix

Removed --allowedTools entirely. The prompt already instructs Claude not to run build commands (CI handles that), and the action needs its injected GitHub tools to function. --max-turns 20 remains as cost control.

Risk

Without an allowlist, Claude could theoretically run arbitrary bash commands. However:

• The action runs with contents: read permissions
• The prompt explicitly says not to run npm/build commands
• The 20-turn limit caps total spend
• The real security boundary is the workflow permissions, not tool restrictions