Add background process management with process tool, wait, PTY, and stdin support

New process registry and tool for managing long-running background processes
across all terminal backends (local, Docker, Singularity, Modal, SSH).

Process Registry (tools/process_registry.py):
- ProcessSession tracking with rolling 200KB output buffer
- spawn_local() with optional PTY via ptyprocess for interactive CLIs
- spawn_via_env() for non-local backends (runs inside sandbox, never on host)
- Background reader threads per process (Popen stdout or PTY)
- wait() with timeout clamping, interrupt support, and transparent limit reporting
- JSON checkpoint to ~/.hermes/processes.json for gateway crash recovery
- Module-level singleton shared across agent loop, gateway, and RL

Process Tool (model_tools.py):
- 7 actions: list, poll, log, wait, kill, write, submit
- Paired with terminal in all toolsets (CLI, messaging, RL)
- Timeout clamping with transparent notes in response

Terminal Tool Updates (tools/terminal_tool.py):
- Replaced nohup background mode with registry spawn (returns session_id)
- Added workdir parameter for per-command working directory
- Added check_interval parameter for gateway auto-check watchers
- Added pty parameter for interactive CLI tools (Codex, Claude Code)
- Updated TERMINAL_TOOL_DESCRIPTION with full background workflow docs
- Cleanup thread now respects active background processes (won't reap sandbox)

Gateway Integration (gateway/run.py, session.py, config.py):
- Session reset protection: sessions with active processes exempt from reset
- Default idle timeout increased from 2 hours to 24 hours
- from_dict fallback aligned to match (was 120, now 1440)
- session_key env var propagated to process registry for session mapping
- Crash recovery on gateway startup via checkpoint probe
- check_interval watcher: asyncio task polls process, delivers updates to platform

RL Safety (environments/):
- tool_context.py cleanup() kills background processes on episode end
- hermes_base_env.py warns when enabled_toolsets is None (loads all tools)
- Process tool safe in RL via wait() blocking the agent loop

Also:
- Added ptyprocess as optional dependency (in pyproject.toml [pty] extra + [all])
- Fixed pre-existing bug: rl_test_inference missing from TOOL_TO_TOOLSET_MAP
- Updated AGENTS.md with process management docs and project structure
- Updated README.md terminal section with process management overview

README.md

@@ -219,9 +219,13 @@ When the agent tries to run a potentially dangerous command (rm -rf, chmod 777,
 
 Reply "yes"/"y" to approve or "no"/"n" to deny. In CLI mode, the existing interactive approval prompt (once/session/always/deny) is preserved.
 
-### 🖥️ Terminal Backend
+### 🖥️ Terminal & Process Management
 
-The terminal tool can execute commands in different environments:
+The terminal tool can execute commands in different environments, with full background process management via the `process` tool:
+
+**Background processes:** Start with `terminal(command="...", background=true)`, then use `process(action="poll/wait/log/kill/write")` to monitor, wait for completion, read output, terminate, or send input. The `wait` action blocks until the process finishes -- no polling loops needed. PTY mode (`pty=true`) enables interactive CLI tools like Codex and Claude Code.
+
+**Execution environments:**
 
 | Backend | Description | Use Case |
 |---------|-------------|----------|