Summary

Fixes #13000

• The boot-md hook now iterates over all configured agents (via listAgentIds) instead of running BOOT.md only for the default agent's workspace.
• runBootOnce() accepts an optional agentId parameter and resolves the per-agent session key when provided.
• Each agent's workspace directory is resolved via resolveAgentWorkspaceDir, so each agent loads its own BOOT.md independently.

Test plan

• New unit test in boot.test.ts verifies per-agent session key resolution (resolveAgentMainSessionKey)
• New test file handler.test.ts verifies the handler iterates over all agents and passes correct workspaceDir + agentId to runBootOnce
• Handler correctly skips non-gateway and non-startup events
• Handler gracefully handles missing cfg in context
• Single-agent (default) configuration still works as before

Greptile Summary

Updated the boot-md hook handler to run BOOT.md for each configured agent at gateway startup instead of only for the default agent. The handler now iterates through all agent IDs via listAgentIds() and resolves each agent's workspace directory independently using resolveAgentWorkspaceDir(). The runBootOnce() function was extended to accept an optional agentId parameter that determines the correct per-agent session key via resolveAgentMainSessionKey().

• Handler now uses listAgentIds() and resolveAgentWorkspaceDir() to iterate over all agents
• runBootOnce() accepts optional agentId parameter for per-agent session key resolution
• Per-agent session key resolution logic properly integrated with existing session management
• Tests verify both multi-agent and single-agent (default) configurations work correctly
• Handler correctly skips execution when cfg is missing from context

Confidence Score: 5/5

• This PR is safe to merge with minimal risk
• The implementation is well-tested with comprehensive unit tests covering both the new per-agent session key resolution and the handler's iteration logic. The changes are focused and backward-compatible (single-agent configurations continue to work). The handler correctly validates required context and gracefully handles missing configuration.
• No files require special attention

_{Last reviewed commit: ecaff9c}