feat: add inference.sh integration (infsh tool + skill) (#1682)

Add inference.sh CLI (infsh) as a tool integration, giving agents
access to 150+ AI apps through a single CLI — image gen (FLUX, Reve,
Seedream), video (Veo, Wan, Seedance), LLMs, search (Tavily, Exa),
3D, avatar/lipsync, and more. One API key manages all services.

Tools:
- infsh: run any infsh CLI command (app list, app run, etc.)
- infsh_install: install the CLI if not present

Registered as an 'inference' toolset (opt-in, not in core tools).
Includes comprehensive skill docs with examples for all app categories.

Changes from original PR:
- NOT added to _HERMES_CORE_TOOLS (available via --toolsets inference)
- Added 12 tests covering tool registration, command execution,
  error handling, timeout, JSON parsing, and install flow

Inspired by PR #1021 by @okaris.

Co-authored-by: okaris <okaris@users.noreply.github.com>

model_tools.py

@@ -95,6 +95,7 @@ def _discover_tools():
         "tools.send_message_tool",
         "tools.honcho_tools",
         "tools.homeassistant_tool",
+        "tools.infsh_tool",
     ]
     import importlib
     for mod_name in _modules: