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

README.md

@@ -1,35 +1,47 @@
 # continuum-schemas
 
-Single source of truth for the Continuum data model. Protobuf definitions in
-`proto/` are compiled into two consumer packages:
+Single source of truth for the Continuum data model. Everything here is
+JSON Schema, compiled into two consumer packages:
 
-- `packages/ts-types` - TypeScript types generated via `ts-proto`, plus
-  hand-written [TypeBox](https://github.com/sinclairzx81/typebox) schemas
-  under `src/schemas/` used for runtime validation in `continuum-backend`'s
-  ElysiaJS routes.
-- `packages/rust-types` - a Rust crate (`continuum-rust-types`) that compiles
-  the same `.proto` files with `prost-build` (via `build.rs`), producing
-  `serde`-derived structs for `continuum-proxy` and `continuum-ai-worker`.
+- `packages/ts-types` - hand-written [TypeBox](https://github.com/sinclairzx81/typebox)
+  schemas under `src/schemas/` used for runtime validation in
+  `continuum-backend`'s ElysiaJS routes.
+- `packages/rust-types` - a Rust crate (`continuum-rust-types`) with
+  hand-written, `serde`-derived structs for `continuum-proxy` and
+  `continuum-ai-worker`.
 
 ## Layout
 
 ```
-proto/continuum/v1/       canonical .proto message definitions
-packages/ts-types/        TypeBox schemas + generated TS proto types
-packages/rust-types/      prost-generated Rust structs (build.rs codegen)
+schemas/continuum/v1/     Continuum's own domain model (PrintJob, Template, ...)
+schemas/bambulab/         Bambu Lab MQTT wire schemas (v1/v2, report + request)
+packages/ts-types/        TypeBox schemas (hand-written, mirrors schemas/)
+packages/rust-types/      serde structs (hand-written, mirrors schemas/)
 ```
 
-## Build
+`schemas/continuum/v1/*.schema.json` is the canonical shape for each
+domain object; `packages/ts-types/src/schemas/` and
+`packages/rust-types/src/lib.rs` both mirror it by hand. There are only
+four small, stable DTOs here (`PrintJob`, `MaterialProfile`,
+`PrintParameters`, `Template`), so keeping two hand-synced copies in sync
+is less overhead than running a codegen pipeline (`protoc`/`ts-proto`/
+`prost-build`) nothing actually consumed - see git history for the
+protobuf version this replaced, and why it was dropped: every service in
+this system talks JSON (JSON Schema for the wire, TypeBox/serde for
+runtime validation), so protobuf's actual value - a single schema compiled
+into a compact **binary** wire format for both languages - never applied.
 
-Requires `protoc` on `PATH` and `npm install` run at the repo root first.
+Whenever a domain schema changes, update all three by hand: the JSON
+Schema file, the TypeBox schema, and the Rust struct.
+
+## Build / verify
+
+Requires `npm install` at the repo root, and a Rust toolchain, first.
 
 ```
 npm install
-npm run build:ts     # protoc + ts-proto -> packages/ts-types/src/generated
-npm run build:rust   # cargo build, runs build.rs -> prost-generated structs
-npm run build        # both
+npm run build:rust   # cargo build, confirms the Rust structs compile
+npm run typecheck     # tsc -b, confirms the TypeBox schemas compile
 ```
 
-Generated TS output under `packages/ts-types/src/generated` is build-derived
-and gitignored. The Rust crate's generated code lands in `OUT_DIR` per
-standard `prost-build` conventions and is never committed.
+There's no `build:ts` step - the TS side is hand-written, not generated.