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/print_job.schema.json

@@ -0,0 +1,40 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://git.octoturge.com/Continuum/continuum-schemas/raw/branch/main/schemas/continuum/v1/print_job.schema.json",
+  "title": "PrintJob",
+  "type": "object",
+  "properties": {
+    "id": { "type": "string", "format": "uuid" },
+    "farmId": { "type": "string", "format": "uuid" },
+    "printerId": { "type": "string", "format": "uuid" },
+    "templateId": { "type": "string", "format": "uuid" },
+    "status": {
+      "type": "string",
+      "enum": [
+        "PRINT_JOB_STATUS_UNSPECIFIED",
+        "PRINT_JOB_STATUS_QUEUED",
+        "PRINT_JOB_STATUS_PRINTING",
+        "PRINT_JOB_STATUS_PAUSED",
+        "PRINT_JOB_STATUS_COMPLETED",
+        "PRINT_JOB_STATUS_FAILED",
+        "PRINT_JOB_STATUS_CANCELLED"
+      ]
+    },
+    "progressPercent": { "type": "number", "minimum": 0, "maximum": 100 },
+    "startedAtUnix": { "type": "integer" },
+    "completedAtUnix": { "type": "integer" },
+    "gcodeFileKey": { "type": "string", "minLength": 1 }
+  },
+  "required": [
+    "id",
+    "farmId",
+    "printerId",
+    "templateId",
+    "status",
+    "progressPercent",
+    "startedAtUnix",
+    "completedAtUnix",
+    "gcodeFileKey"
+  ],
+  "additionalProperties": false
+}