mcp, cli: list each command's parameters as JSON Schema

CommandSpec::listing gives id, label, the parameter doc and the schema; MCP
list_commands, the control channel's engine.commands and the new
fieldcraft-cli commands --json use it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UhhZMBTviDQxZvwnyP89fo

docs/control-protocol.md

@@ -26,7 +26,7 @@ checked and clamped (drag steps, wheel lines, window size); `ui.render` refuses
 |---|---|---|
 | `engine.execute` | `command`: command id, `params`: JSON object | the command's result |
 | `engine.script` | `commands`: `[{command, params}, …]` | stops at the first error; `journal`: commands that changed the model so far |
-| `engine.commands` | — | every command: `id`, `label`, `params` (the parameter documentation) |
+| `engine.commands` | — | every command: `id`, `label`, `params` (the parameter documentation) and `schema` (its parameters as JSON Schema) |
 
 Commands never open forms or file pickers when run this way. `fieldcraft-cli commands` prints the
 same registry. `file.sample {name}` opens a sample (`parts`, `cantilever`, `impact`) and

docs/mcp.md

@@ -91,7 +91,7 @@ software on the computer.
 
 | Tool | Arguments | What it does |
 |---|---|---|
-| `list_commands` | `filter?` | Every command with its label and parameter documentation; `filter` matches id and label. |
+| `list_commands` | `filter?` | Every command with its label, parameter documentation and `schema` (its parameters as JSON Schema: types, units as `x-dimension`, defaults, required fields, one-of variants); `filter` matches id and label. |
 | `execute` | `command`, `params?` | Run any command (`list_commands`). A failure leaves the model unchanged and names what to fix. |
 | `batch` | `commands: [{command, params}]` | Run steps in order, stop at the first error; the reply has every result and the failing step (`failed.index`, `failed.command`, `failed.error`). Steps before it stay applied (`undo` takes them back). |
 | `inspect_model` | — | `model.info` (counts, units, definitions), `model.activity` (the step table) and `geometry.bodies` (bodies with measures and persistent face names, which sets name as `{body, face}`). |