Add Outline API client library foundation

Implements a first vertical slice of the Outline RPC API (auth, documents,
collections, users) covering the structural patterns used across the whole
API: single object, paginated list, tree, create/update, delete, search.
Chosen as the basis for future CLI and GUI clients built on top of this crate.

- Handwritten client (not codegen) against the vendored OpenAPI spec, since
  Outline's API is uniformly POST /api/<resource>.<action> with JSON bodies
  and inline/anonymous schemas that generators handle poorly
- Async (reqwest + tokio) Client, cheaply cloneable, no &mut self methods
- thiserror-based Error with ErrorKind classification and boxed API error
  context; forward-compatible models (unknown fields ignored, unknown
  string-enum values preserved via a catch-all variant) since the API is
  unversioned and self-hosted instances vary in age
- Pagination via Page<T>/Paginator with next_page/collect_all/into_stream
- wiremock-based test suite plus a spec-coverage test guarding against typos
  in RPC method names

Cargo.toml

@@ -0,0 +1,47 @@
+[package]
+name = "outline-sdk"
+version = "0.1.0"
+edition = "2024"
+rust-version = "1.85"
+license = "MIT OR Apache-2.0"
+description = "Async Rust client for the Outline (getoutline.com) knowledge base API"
+keywords = ["outline", "wiki", "api", "client", "knowledge-base"]
+categories = ["api-bindings", "asynchronous"]
+readme = "README.md"
+
+[lib]
+name = "outline"
+
+[features]
+default = ["rustls-tls", "stream"]
+rustls-tls = ["reqwest/rustls"]
+native-tls = ["reqwest/native-tls"]
+stream = ["dep:futures-core", "dep:futures-util", "reqwest/stream"]
+multipart = ["reqwest/multipart"]
+tracing = ["dep:tracing"]
+uuid = ["dep:uuid"]
+
+[dependencies]
+reqwest = { version = "0.13", default-features = false, features = ["json", "http2", "charset"] }
+serde = { version = "1.0.181", features = ["derive"] }
+serde_json = "1"
+thiserror = "2"
+url = "2"
+http = "1"
+chrono = { version = "0.4", default-features = false, features = ["serde", "std", "clock"] }
+secrecy = "0.10"
+futures-core = { version = "0.3", optional = true }
+futures-util = { version = "0.3", optional = true, default-features = false }
+bytes = "1"
+tracing = { version = "0.1", optional = true }
+uuid = { version = "1", optional = true, features = ["serde"] }
+
+[dev-dependencies]
+tokio = { version = "1", features = ["macros", "rt-multi-thread"] }
+wiremock = "0.6"
+serde_json = "1"
+futures-util = "0.3"
+http = "1"
+
+[package.metadata.docs.rs]
+all-features = true