feat(openapi): add OpenAPI 3.x introspection adapter; bump workspace to 0.2.0

- Add OpenApiAdapter with spec caching, operationId + METHOD/path resolution,
  args binding, dual rate limiting, and params.server.url override
- Add openapiv3 and serde_yaml workspace dependencies
- Update CHANGELOG with 0.2.0 entry
- Update mdBook docs: introduction.md and graph/adapters.md OpenAPI section
- Bump all README version references from 0.1 to 0.2

Author: greysquirr3l

CHANGELOG.md

@@ -7,6 +7,20 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [0.2.0] - 2026-03-16
+
+### Added
+
+- `stygian-graph`: `OpenApiAdapter` — OpenAPI 3.x introspection adapter (`kind = "openapi"`)
+  - Fetches and caches parsed OpenAPI specs (JSON or YAML) per spec URL for the lifetime of the adapter
+  - Resolves operations by `operationId` (e.g. `"listPets"`) or `"METHOD /path"` syntax (e.g. `"GET /pet/findByStatus"`)
+  - Binds `params.args` to path parameters (substituted into the URL template), query parameters, and request body
+  - Delegates all HTTP calls to the inner `RestApiAdapter`, inheriting full auth support, retries, and 429 handling
+  - Optional proactive rate limiting via `params.rate_limit` (sliding-window or token-bucket, same shape as GraphQL rate limiter)
+  - `params.server.url` overrides `servers[0].url` from the spec at runtime
+  - Two new workspace dependencies: `openapiv3 = "1"`, `serde_yaml = "0.9"` (always compiled; pure Rust)
+- `book`: OpenAPI adapter section added to [Built-in Adapters](./graph/adapters.md)
+
 ## [0.1.20] - 2026-03-16
 
 ### Added

Cargo.lock

@@ -7,7 +7,7 @@ members = [
 ]
 
 [workspace.package]
-version = "0.1.20"
+version = "0.2.0"
 edition = "2024"
 rust-version = "1.94.0"
 authors = ["Nick Campbell <s0ma@protonmail.com>"]
@@ -73,6 +73,10 @@ uuid = { version = "1", features = ["v4", "serde"] }
 # Data pipeline
 csv = "1.3"
 
+# OpenAPI spec parsing
+openapiv3 = "1"
+serde_yaml = "0.9"
+
 # WASM plugins (optional heavy dep)
 wasmtime = { version = "42", default-features = false, features = ["runtime", "cranelift", "component-model"] }
 

Cargo.toml

@@ -99,8 +99,8 @@ Add to your `Cargo.toml`:
 
 ```toml
 [dependencies]
-stygian-graph = "0.1"
-stygian-browser = "0.1"  # optional, for JavaScript rendering
+stygian-graph = "0.2"
+stygian-browser = "0.2"  # optional, for JavaScript rendering
 tokio = { version = "1", features = ["full"] }
 ```
 
@@ -230,6 +230,6 @@ Built with:
 
 ---
 
-**Status**: Active development | Version 0.1.15 | Rust 2024 edition | 694 tests | Linux + macOS
+**Status**: Active development | Version 0.2.0 | Rust 2024 edition | Linux + macOS
 
 For detailed documentation, see the [project docs site](https://greysquirr3l.github.io/stygian).