feat(glyph): tune transmission settings for RPC performance

[stackptr]

Summary

• Increase Transmission disk write cache from default 4MB to 256MB to reduce I/O contention blocking the single-threaded RPC event loop
• Enable download queue (max 5 active, 30min stall timeout) to limit concurrent disk I/O
• Addresses slow web UI load times (~9-17s) caused by 2000+ loaded torrents

Context

Transmission 4.1.1 has a confirmed performance regression with large torrent counts. The root cause is synchronous disk I/O blocking the RPC thread (#2462, targeted for 5.0). These settings reduce I/O pressure as a mitigation. If insufficient, next step is pinning to transmission 4.0.6.

Test plan

• Deploy to glyph via nh os switch
• Verify curl -w "%{time_total}\n" -o /dev/null -s http://localhost:9091 response time improves
• Confirm torrents.zx.dev loads in reasonable time from browser

🤖 Generated with Claude Code

[stackptr]

These changes don't fix the issue but are probably sensible to have anyways

[Sekkyo]

@stackptr That's my main question. How was this area of performance degraded so much between 4.0.6 and 4.1? 4.0.6 still works great. What did 4.1 introduce in this area that caused such I/O contention blocking?