fix(memory): add TTL, LRU eviction, and ring buffers to prevent memory leaks

[Stranmor]

Summary

Addresses memory leak issues reported in #10913, #9140, #5363.

This PR adds cleanup mechanisms to prevent unbounded memory growth in long-running sessions:

Changes

Component	Fix	Details
ACPSessionManager	TTL + LRU	1h TTL, 50 session limit, 5min cleanup interval
Instance cache	TTL + LRU	30min idle TTL, 10 instance limit, auto-dispose
LSP clients	Max limit	20 client limit, oldest-first eviction
PTY buffers	RingBuffer	O(1) append instead of string concatenation

Technical Details

ACPSessionManager (acp/session.ts)

• Added SessionEntry wrapper with lastAccess timestamp
• Periodic cleanup every 5 minutes removes sessions idle >1 hour
• Hard limit of 50 sessions with LRU eviction

Instance cache (project/instance.ts)

• Added CacheEntry wrapper with lastAccess tracking
• evictIdleInstances() called on new instance creation
• Properly disposes State when evicting idle instances

LSP clients (lsp/index.ts)

• Added MAX_LSP_CLIENTS = 20 limit
• Evicts oldest client when limit reached
• Graceful shutdown of evicted clients

PTY buffers (pty/index.ts)

• New RingBuffer class with chunk-based storage
• Avoids repeated large string allocations
• O(1) append, automatic trimming to limit

Testing

• TypeScript compiles without errors in changed files
• Manual testing with long-running sessions
• Memory profiling before/after

Related Issues

• Fixes fix: multiple memory leaks in long-running sessions #10913 (memory leaks in long-running sessions)
• Addresses Memory leak: Unbounded caches grow without limit #9140 (unbounded caches)
• Addresses opencode eating 70gb of memory? #5363 (high memory usage)

[github-actions]

The following comment was made by an LLM, it may be inaccurate:

Based on my search results, I found 3 potentially related PRs that address similar memory leak issues:

1. PR fix(memory): resolve 6 memory leak issues in long-running sessions #12053 - "fix(memory): resolve 6 memory leak issues in long-running sessions"

   • Directly addresses the same category of problems (memory leaks in long-running sessions)

2. PR fix(opencode): resolve multiple memory leaks in long-running sessions #10914 - "fix(opencode): resolve multiple memory leaks in long-running sessions"

   • Also targets memory leaks in long-running sessions with similar scope

3. PR feat(util): Add bounded LRU cache utility #9141 - "feat(util): Add bounded LRU cache utility"

   • Provides LRU cache implementation that could be related to the eviction mechanisms in PR fix(memory): add TTL, LRU eviction, and ring buffers to prevent memory leaks #12259

These PRs likely overlap with the memory leak fixes in PR #12259. You should review PR #12053 in particular, as it appears to address the same core issue of resolving memory leaks in long-running sessions.