perf: Add MAXLEN to Redis streams to prevent unbounded memory growth

[smoreinis]

Summary

• Adds REDIS_STREAM_MAXLEN environment variable (default: 10,000)
• Configures xadd() with maxlen and approximate=True for O(1) trimming
• Prevents Redis memory exhaustion from long-running task event streams

Problem

Redis streams were created without any size limit, causing unbounded memory growth over time. A long-running task could accumulate unlimited events in its stream.

Solution

Added maxlen parameter to xadd() calls with configurable limit via environment variable. Uses approximate=True for better performance (O(1) vs O(N) trimming).

Test Results

Metric	Value
Before xadd	12,000 entries
After xadd with maxlen	10,001 entries
Entries trimmed	~2,000

How to Verify

# Check stream length before/after
redis-cli XLEN task:<task_id>

# Monitor memory usage
redis-cli INFO memory | grep used_memory_human

Files Changed

• src/config/environment_variables.py - Added REDIS_STREAM_MAXLEN env var
• src/adapters/streams/adapter_redis.py - Added maxlen to xadd()

[smoreinis]

Thoughts on this? The existing comment already said "Add to Redis stream with a reasonable max length" so I feel like not having one here was an oversight but I don't have a good sense whether or not 10k here is reasonable or if something like 1k is a better default.