docs: correct the result contract and document the _for_cli Blender lookup - #1

Two parts of the skill don't match what the pinned server (v1.0.3, 2cea8d5) actually does.

Bug

1. SKILL.md says to assign JSON-serializable output to result, and the server's own instructions (prompts.yml) suggest returning "dicts, lists". The add-on only accepts a dict: result = [1.5, 2.5, 3.5] or result = 4 comes back as The `result` variable must be a dict, not list. That error arrives after the code has already run, so an agent that retries can apply the same edit twice.
2. The six *_for_cli tools (execute_blender_code_for_cli and the five get_blendfile_summary_*_for_cli tools) fail when Blender comes from the blender.org macOS app or Windows installer, since neither puts a blender command on PATH: Blender executable not found at 'blender'. Set the BLENDER_PATH environment variable to the correct path. Setting BLENDER_PATH in a shell or .env, as that message says, doesn't reach the server under Hermes, and the docs don't mention any of this.

Cause

1. mcp_to_blender_server.py in the add-on runs the code, then rejects any result that isn't a dict. execute_blender_code sends strict_json=False, so Blender objects inside the dict are converted with repr rather than failing.
2. Those tools run blender --background from BLENDER_PATH, else from PATH (blmcp/tools_helpers/blender_cli.py). Hermes starts MCP servers with a filtered environment (_build_safe_env in tools/mcp_tool_config.py) that keeps PATH but drops shell and .env variables such as BLENDER_PATH, and portable mcp.json values aren't ${VAR}-interpolated, so this package can't forward it either.

Fix

Docs only; mcp.json and plugin.json are unchanged. SKILL.md states the dict contract with an example, says a rejected result has still run, and tells the agent that _for_cli tools take an absolute path and need blender on the server's PATH, so it points the user to setup instead of retrying. setup.md gets a Failures entry with the cause and the fix, and the README lists the optional prerequisite.

Verification

• Ran the add-on's own _execute_code from 2cea8d5 outside Blender, with only bpy.ops stubbed: list and int results return the dict error, {"location": [1.5, 2.5, 3.5]} returns ok, {"obj": object()} returns ok with a repr string, and a snippet that sets a global and then assigns a list returns the error with the global still set.
• Installed the plugin from main (d1929b5, same mcp.json as this branch) into a temporary HERMES_HOME with current Hermes main (71a2fe3) using the README commands, then started the server the way _run_stdio does and called get_blendfile_summary_path_info_for_cli:
  • BLENDER_PATH exported in the shell, pointing at an existing executable: missing from the server's environment, and the tool fails with Blender executable not found at 'blender'.
  • BLENDER_PATH in HERMES_HOME/.env: same result.
  • A blender executable on PATH: the server runs it with --background <file>.
• The server lists 26 tools; the 6 that take blend_file all end in _for_cli.
• hermes plugins validate --json on this branch: ok, no warnings. The skill still loads, and the translated MCP launch config is identical to main.
• Blender isn't installed on the machine I tested on, so I haven't run a _for_cli tool against a real Blender.