P1: CI: require status checks on main and add a build badge (pipeline shipped in #33)

[macanderson]

Problem

The repository has no CI — .github/ contains issue templates and funding config, but no workflows/ directory. For a project whose core pitch is "conformance is a test you run in CI", the spec repo itself not running conformance in CI is a credibility gap, and every normative guarantee (schema ↔ types agreement, examples validity, the suite catching misbehavior) is currently re-verified only by hand.

Proposal

Add a GitHub Actions workflow running on every PR and push to main:

Rust jobs

• cargo fmt --check — landed in Pre-freeze normative sweep: SPEC.md, canonical token accounting, conformance that actually catches things #33
• cargo clippy --workspace --all-targets -- -D warnings — landed in Pre-freeze normative sweep: SPEC.md, canonical token accounting, conformance that actually catches things #33
• cargo test --workspace — landed in Pre-freeze normative sweep: SPEC.md, canonical token accounting, conformance that actually catches things #33
• MSRV check: build with the pinned rust-version = "1.90" toolchain, not just stable — landed in Pre-freeze normative sweep: SPEC.md, canonical token accounting, conformance that actually catches things #33

Protocol witness jobs (the ones unique to this repo)

• Conformance green: run contextgraph-inspect against the bundled contextgraph-example-docs fixture — all 5 checks must pass. — landed in Pre-freeze normative sweep: SPEC.md, canonical token accounting, conformance that actually catches things #33; the workflow also runs the host-conformance job added in Pre-freeze: normative completeness + enforcement + host conformance (top-10 build) #60
• Conformance red: run each --misbehave mode and assert the matching check fails. The suite's claim that it "genuinely catches broken providers rather than rubber-stamping everything" (docs/protocol-advantages.md §6) becomes machine-verified on every PR. — landed in Pre-freeze normative sweep: SPEC.md, canonical token accounting, conformance that actually catches things #33
• Schema ↔ types golden test: validate examples/reference-messages.json and every line of examples/full-stdio-session.ndjson against schema/contextgraph-envelope.schema.json (schema/validate-examples.py already exists — wire it in). Additionally, round-trip the reference messages through contextgraph-types serde in a Rust test so a drift between the Rust types and the JSON Schema turns a PR red instead of silently shipping two divergent sources of truth. — landed in Pre-freeze normative sweep: SPEC.md, canonical token accounting, conformance that actually catches things #33

Site job

• pnpm build in site/ so docs-site breakage is caught at PR time. — landed in ci(site): promote docs-site build to a hard gate #62 (promoted from advisory to a hard gate)

Acceptance criteria

• A PR that changes a wire type without updating the schema/examples fails CI — landed in Pre-freeze normative sweep: SPEC.md, canonical token accounting, conformance that actually catches things #33
• A PR that breaks any --misbehave detection fails CI — landed in Pre-freeze normative sweep: SPEC.md, canonical token accounting, conformance that actually catches things #33
• Branch protection on main requires the workflow
• README carries a build badge

---

Remaining scope (2026-07-26): the pipeline itself is complete — all four job groups run on every PR. What is missing is the gate: branch protection on main 404s and the active ruleset carries no required_status_checks, so every job above is advisory at merge time. Close this by adding required_status_checks naming the workflow's jobs, plus the README badge.

[macanderson]

Re-verified 2026-07-26 against origin/main @ 1ee9b1c.

What landed: the Problem section's premise is dead. ci.yml landed in PR #33 with all four job groups — fmt/clippy/test/msrv, conformance green and --misbehave red plus the host suite, schema validation, and the site gate.

What survives: the gate itself. Branch protection 404s and the active ruleset carries no required_status_checks, so every one of those jobs is advisory at the merge point — a red run does not stop a merge, which is the property the issue was actually asking for. There is also still no README badge.

Recommended scope: narrow to the two open boxes — add required_status_checks naming the ten jobs, and add a README badge. The Problem section is now entirely false and should be rewritten rather than left standing.