Implement voting countdown system for "-" comments

[konard]

Summary

This PR implements a voting countdown system to prevent users from responding with "-" to another "-" comment within a specified time period (5 minutes by default), as requested in issue #62.

Key Features

• Countdown mechanism: Users must wait 5 minutes between "-" votes to prevent spam/harassment
• Per-user tracking: Each user has their own countdown timer
• Persistent storage: Uses FileStorage to remember voting timestamps across bot restarts
• Warning messages: Bot posts informative comments when users violate the countdown rule
• Non-disruptive: Only affects "-" comments, doesn't interfere with other bot functionality

Implementation Details

New Components:

• VotingCountdownTrigger: Main logic for detecting and enforcing countdown rules
• GitHubStorage.GetIssueComments(): Method to retrieve issue comments for analysis
• Voting timestamp tracking using FileStorage with format: voting_countdown_tracking_{repoId}_{issueNumber}

Integration:

• Added trigger to IssueTracker in Program.cs alongside existing triggers
• Configurable countdown period (defaults to 5 minutes)
• Graceful error handling to prevent bot crashes

How It Works

1. Detection: Bot monitors all issues for "-" comments
2. Analysis: When "-" comments are found, checks timing between consecutive votes
3. Enforcement: If a user votes "-" too quickly after their previous "-" vote, posts a warning
4. Persistence: Saves user voting timestamps to prevent circumvention via bot restart

Test Plan

• ✅ Code compiles successfully with no errors
• ✅ Created experiment script demonstrating countdown logic correctness
• ✅ Tested scenarios: valid timing, invalid timing, multiple users
• ✅ Verified integration with existing bot architecture

Example Warning Message:

@username Please wait 5 minutes before responding with "-" to another "-" comment. This helps maintain civil discussion. Your comment was posted too quickly after a previous "-" vote.

Files Changed

• csharp/Storage/RemoteStorage/GitHubStorage.cs: Added comment retrieval method
• csharp/Platform.Bot/Triggers/VotingCountdownTrigger.cs: Main countdown logic (new)
• csharp/Platform.Bot/Program.cs: Integrated new trigger
• experiments/: Added test scripts to validate implementation

Fixes #62

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