docs: add ACP and internal systems implementation guides

- add ACP user and developer docs covering setup, lifecycle, callbacks,
  permissions, tool rendering, and runtime behavior
- add developer guides for agent loop, provider runtime resolution,
  prompt assembly, context caching/compression, gateway internals,
  session storage, tools runtime, trajectories, and cron internals
- refresh architecture, quickstart, installation, CLI reference, and
  environments docs to link the new implementation pages and ACP support

website/docs/developer-guide/tools-runtime.md

@@ -0,0 +1,65 @@
+---
+sidebar_position: 9
+title: "Tools Runtime"
+description: "Runtime behavior of the tool registry, toolsets, dispatch, and terminal environments"
+---
+
+# Tools Runtime
+
+Hermes tools are self-registering functions grouped into toolsets and executed through a central registry/dispatch system.
+
+Primary files:
+
+- `tools/registry.py`
+- `model_tools.py`
+- `toolsets.py`
+- `tools/terminal_tool.py`
+- `tools/environments/*`
+
+## Tool registration model
+
+Each tool module calls `registry.register(...)` at import time.
+
+`model_tools.py` is responsible for importing/discovering tool modules and building the schema list used by the model.
+
+## Toolset resolution
+
+Toolsets are named bundles of tools. Hermes resolves them through:
+
+- explicit enabled/disabled toolset lists
+- platform presets (`hermes-cli`, `hermes-telegram`, etc.)
+- dynamic MCP toolsets
+- curated special-purpose sets like `hermes-acp`
+
+## Dispatch
+
+At runtime, tools are dispatched through the central registry, with agent-loop exceptions for some agent-level tools such as memory/todo/session-search handling.
+
+## Terminal/runtime environments
+
+The terminal system supports multiple backends:
+
+- local
+- docker
+- ssh
+- singularity
+- modal
+- daytona
+
+It also supports:
+
+- per-task cwd overrides
+- background process management
+- PTY mode
+- approval callbacks for dangerous commands
+
+## Concurrency
+
+Tool calls may execute sequentially or concurrently depending on the tool mix and interaction requirements.
+
+## Related docs
+
+- [Toolsets Reference](../reference/toolsets-reference.md)
+- [Built-in Tools Reference](../reference/tools-reference.md)
+- [Agent Loop Internals](./agent-loop.md)
+- [ACP Internals](./acp-internals.md)