Isolate memory by channel/chat to prevent cross-chat leakage

[lawyered0]

Summary

This PR closes a critical data-isolation issue by scoping agent memory per channel + chatID.

Critical issue addressed

Memory context was previously shared across chats, which allowed data from one conversation to leak into another conversation’s prompt context.

What changed

• Updated internal/agent/loop.go:
  • Memory store selection now scopes by sanitized channel and chatID for all channels, including cli.
  • Per-message memory context and recent memories now come from the scoped store.
  • write_memory tool is pointed at the active scoped memory store before tool execution.
• Updated internal/agent/tools/write_memory.go:
  • Added runtime store switching support (SetStore) with synchronization.
• Added regression coverage in internal/agent/loop_memory_scope_test.go:
  • verifies isolation for Telegram chat IDs
  • verifies isolation for CLI chat IDs
• Updated related tests to use scoped reads and temp workspaces:
  • internal/agent/loop_processdirect_test.go
  • internal/agent/loop_remember_test.go
  • internal/agent/loop_write_memory_test.go
  • plus other loop tests using explicit temp workspaces for isolation hygiene.

Validation

• go test ./internal/agent -run "MemoryIsScoped|RemembersToday|ExecutesWriteMemoryToolCall" -count=1
• go test ./internal/agent/tools -run WriteMemory -count=1
• go test -race ./internal/agent -run "MemoryIsScoped|RemembersToday|ExecutesWriteMemoryToolCall|ProcessDirectExecutesToolCall" -count=1
• go test ./...