Drop Protobuf; move continuum/v1 domain model to JSON Schema

Nothing imported the proto-generated code (zero references to
continuum-rust-types or @continuum/ts-types's proto export in any
consumer repo), and protobuf's real value - one schema compiled to a
compact binary wire format for both languages - never applied: BE<->proxy
and FE<->BE are both JSON. Also fixes 8 broken $ref paths in the bambulab
schemas and a root tsconfig.json that was sweeping the gitignored
examples/ directory into typecheck.

- proto/continuum/v1/*.proto -> schemas/continuum/v1/*.schema.json
- packages/rust-types: hand-written serde structs instead of
  prost-build codegen
- packages/ts-types: drop the generated/ proto barrel export, keep the
  hand-written TypeBox schemas as the TS source of truth
- root package.json: drop build:ts, protoc, ts-proto

schemas/continuum/v1/material.schema.json

@@ -0,0 +1,25 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://git.octoturge.com/Continuum/continuum-schemas/raw/branch/main/schemas/continuum/v1/material.schema.json",
+  "title": "MaterialProfile",
+  "type": "object",
+  "properties": {
+    "id": { "type": "string", "format": "uuid" },
+    "name": { "type": "string", "minLength": 1 },
+    "filamentType": { "type": "string", "minLength": 1 },
+    "nozzleTempC": { "type": "number" },
+    "bedTempC": { "type": "number" },
+    "densityGCm3": { "type": "number" },
+    "colorHex": { "type": "string", "pattern": "^#[0-9a-fA-F]{6}$" }
+  },
+  "required": [
+    "id",
+    "name",
+    "filamentType",
+    "nozzleTempC",
+    "bedTempC",
+    "densityGCm3",
+    "colorHex"
+  ],
+  "additionalProperties": false
+}