feat(mcp): natural-language measurements for tool inputs via @pascal-app/lingo

Measurement/angle parameters on the scene tools now accept a bare number OR a
natural-language string ("6 in", "180cm", "45°", "1.57rad"), canonicalized to
the unit the handler already expects (meters for length, radians/degrees for
angles) with min/max bounds and model-readable errors. Makes LLM tool calls
safer — "6 in" no longer has to be pre-converted to 0.1524, and a bad value is
rejected with a message the model can self-correct from.

A shared `measurement(kind, unit)` zod field wraps lingo's parseQuantity as a
`number | string` union+transform; numbers pass through unchanged (backward
compatible), so no handler changes were needed. Covers create_wall, cut_opening,
place_item, create_level, create_story_shell, create_roof,
create_stair_between_levels, create_room, add_door, add_window, photo_to_scene.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

packages/mcp/src/tools/create-wall.ts

@@ -5,14 +5,15 @@ import { z } from 'zod'
 import type { SceneOperations } from '../operations'
 import { ErrorCode, throwMcpError } from './errors'
 import { publishLiveSceneSnapshot } from './live-sync'
+import { measurement } from './measurement'
 import { NodeIdSchema, Vec2Schema } from './schemas'
 
 export const createWallInput = {
   levelId: NodeIdSchema,
   start: Vec2Schema,
   end: Vec2Schema,
-  thickness: z.number().positive().optional(),
-  height: z.number().positive().optional(),
+  thickness: measurement('length', 'm', { min: 0, description: 'Wall thickness.' }).optional(),
+  height: measurement('length', 'm', { min: 0, description: 'Wall height.' }).optional(),
 }
 
 export const createWallOutput = {