Raise character limits and document optional Blender MCP

docs/blender-mcp.md

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+# Optional Blender MCP
+
+Status: **optional interactive tooling, not a build dependency.** Blender MCP is
+useful for exploring a local part scene, moving the viewport and iterating on a
+head/hand mesh without a manual UI walkthrough. The authoritative asset
+pipeline remains the headless CLI plus `audit`/`fit`/`inspect`; CI, tests and
+release builds must continue to work with no Blender process and no MCP server.
+
+This project does not vend the third-party addon or pin a runtime MCP
+dependency. Install it outside the repository and keep generated scenes under
+`tmp/`.
+
+## What it adds
+
+With Blender MCP connected, an agent can:
+
+- query the current scene and object data;
+- run small `bpy` snippets through the MCP bridge;
+- capture a viewport screenshot for visual checks;
+- inspect or modify a local part scene before exporting a GLB.
+
+It does **not** replace:
+
+- `python3 tools/blender_assets.py audit/fit/inspect`;
+- `python3 tools/npc_proportions.py`;
+- the Godot capture and smoke gates;
+- the project's licence/provenance review.
+
+## Prerequisites
+
+- Blender 5.2 LTS, installed as the `org.blender.Blender` flatpak (the project
+  standard).
+- An MCP-capable client.
+- The upstream [BlenderMCP addon](https://github.com/ahujasid/blender-mcp)
+  (`addon.py`) and its MCP server.
+- `uv`/`uvx` if you use the server's `uvx blender-mcp` launcher; a local install
+  of the server package is equally valid.
+
+Check the upstream README for the current package/addon version and any command
+changes before installing. Do not copy the addon into this repository.
+
+## Setup
+
+### 1. Install the Blender addon
+
+1. Download or clone the upstream BlenderMCP project.
+2. In Blender: **Edit → Preferences → Add-ons → Install from Disk**, select
+   `addon.py` from that checkout.
+3. Enable **Interface: Blender MCP**.
+4. Open the 3D View sidebar (N panel), find the **BlenderMCP** tab, and click
+   **Connect to MCP server**. The default server listens on
+   `localhost:9876`.
+
+The addon must be running inside the Blender process that has the scene open.
+Starting a second Blender instance does not connect the first one.
+
+### 2. Configure the MCP client
+
+For Pi, add the server at user scope so it is not committed into the project:
+
+```bash
+pi mcp add blender -- uvx blender-mcp
+pi mcp list
+```
+
+Then start/reload Pi and use `/mcp` to inspect the connection. Other clients
+use their normal MCP server configuration. A generic JSON example:
+
+```json
+{
+  "mcpServers": {
+    "blender": {
+      "command": "uvx",
+      "args": ["blender-mcp"]
+    }
+  }
+}
+```
+
+For a client with a different config schema, use the equivalent server command
+and keep the server name `blender`. Restart/reload the client after adding it,
+then request the tool list and run a harmless `get_scene_info` before editing.
+
+### 3. Connect through the flatpak
+
+Start Blender through the project's normal flatpak command, open the local part
+scene, and connect from the sidebar. If the client cannot reach the addon:
+
+- confirm the addon panel says connected;
+- confirm the client is launching the MCP server, not just a shell;
+- check port `9876` is not occupied;
+- if the flatpak sandbox is blocking localhost networking, grant network
+  permission only for this interactive use, for example:
+  `flatpak override --user --share=network org.blender.Blender`
+  (review the permission change afterwards; do not add it to CI or build
+  scripts).
+- restart both the MCP client and Blender after changing the addon or config.
+
+## Recommended part-workflow
+
+1. Create a local scene, for example
+   `tmp/npc-parts/npc_casual/head.blend`, or open a copy of an exported part GLB.
+   Never save over the tracked `assets/models/npc/npc_base.blend`.
+2. Ask the MCP client for `get_scene_info`, then inspect the object/bone/mesh
+   names it reports.
+3. Use `execute_blender_code` for small, reversible edits. Prefer adding a new
+   object or modifier over deleting existing geometry; keep a backup copy.
+4. Use `get_viewport_screenshot` after camera/material changes to check the
+   head/face/hand before exporting.
+5. Export a **local** GLB under `tmp/npc-parts/`, not directly into
+   `assets/models/`.
+6. Run the normal gates on the exported file:
+
+   ```bash
+   flatpak run org.blender.Blender --background \
+     --python "$PWD/tools/blender_assets.py" -- \
+     inspect --file "$PWD/tmp/npc-parts/head.glb" --category npc --json
+   python3 tools/blender_assets.py audit
+   python3 tools/blender_assets.py fit
+   python3 tools/npc_proportions.py report
+   ```
+
+7. Only after the part is reviewed and the contract passes should it be
+   assembled into a character and rebuilt through the headless pipeline.
+
+## Safety and project rules
+
+- MCP is **not** part of `project.godot`, the build, CI, tests, release packages
+  or runtime.
+- Do not commit `.blend` part scenes, MCP configuration, API keys or generated
+  previews. The working set stays in `tmp/`.
+- Do not use MCP to bypass the contract, budgets, AO/UV rules or licence gate.
+- The 13 core bones must remain at their rest positions; extra optional bones
+  are allowed only if `NpcAvatar` and the audit/tests still pass.
+- Prefer scripted headless changes for reproducible work; MCP is for the
+  interactive exploration and review that is awkward in a one-shot script.
+- If MCP is unavailable, use the headless CLI and document the manual step; never
+  make the project depend on MCP being present.
+
+## Troubleshooting
+
+| Symptom | Check |
+| --- | --- |
+| Client cannot find `blender` | MCP client config path/schema; restart client; confirm server command exists |
+| `Connection refused` | Addon **Connect to MCP server** pressed; Blender still running; port 9876 |
+| Tools return stale scene data | Refresh scene/object query after edits; restart the connection if needed |
+| Flatpak cannot reach localhost | Check flatpak network permission; grant only for interactive use |
+| Changes look wrong in export | Re-import the GLB with `inspect`; check transforms, scale, UVs and materials |
+| Contract audit fails | Fix the mesh/bones first; do not edit the audit expectations around a broken asset |