[nofuturekid]

Fixes #178

Task 1 of docs/superpowers/plans/2026-11-13-obsbot4linux-w0-contracts.md.

What changed

• New crate crates/obsbot-proto (serde, serde_json, schemars): ids, values, description (types and builders), state (State, Patch, path helpers), message (Request with from_line, Reply, Event, ErrorBody, ErrorCode), and stubs for client, validate (holding Refusal) and schema.
• Root Cargo.toml: member crates/obsbot-proto; workspace dependencies obsbot-proto and schemars = "1.2". Cargo.lock gains schemars and its dependencies.
• tests/types.rs with tests/golden/types.jsonl: every golden line round-trips byte for byte through its type (24 type names).
• Files are the plan's code, put in place unchanged. No camera I/O, no version change, no CHANGELOG line (no user-visible change).

Adaptations to the plan

• Root Cargo.toml lists its members explicitly (no crates/* glob), so "crates/obsbot-proto" was added to members. serde and serde_json were already in [workspace.dependencies] in the plan's form. No other adaptation was needed.

Verification

• Before the types existed: cargo test -p obsbot-proto --test types failed to compile (unresolved Verb, Support, ... ), as the plan expects.
• cargo test -p obsbot-proto: 10 unit tests (ids 2, values 4, state 4) and 4 tests in tests/types.rs pass.
• Whole workspace cargo test --locked: all pass (171 + 25 + 10 + 4 + 2 + 1 tests).
• cargo fmt --check: clean. cargo clippy --workspace --all-targets --locked -- -D warnings: clean.
• Forward compatibility: unknown Support, SettingType, Unit, ErrorCode values and an unknown event type parse (additive_values_from_a_newer_daemon_still_parse).
• Mutation checks (code broken, test seen to fail, code restored):
  • values::number no longer writes integral numbers as integers: integral_numbers_are_written_without_a_fraction and rounding_removes_float_noise fail.
  • catch-all Support::Other made #[serde(skip)] instead of #[serde(untagged)]: every_golden_line_round_trips_byte_equal and additive_values_from_a_newer_daemon_still_parse fail.

Contract note (spec 10.1): these types are the protocol 2 contract; later tasks and tracks build on them without changing them.