docs: update README and CHANGELOG for v0.7.0

Add capabilities caching API examples (loadCapabilities, KnownExtension),
getLyricsBySongId usage example, updated endpoint table, and full v0.7.0
CHANGELOG entry covering all new types, fields, and public inits.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: MathieuDubart

CHANGELOG.md

@@ -7,6 +7,47 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ---
 
+## [0.7.0] — 2026-05-04
+
+### Added
+
+- **OpenSubsonic server identification** — `ServerCapabilities` now exposes `serverType` and `serverVersion` populated from the `type` / `serverVersion` fields returned by OpenSubsonic-compliant servers (Navidrome, gonic, …).
+
+- **`KnownExtension` enum** — compile-time–safe identifiers for every OpenSubsonic extension defined in the spec (`songLyrics`, `apiKeyAuthentication`, `playbackReport`, `transcodeOffset`, `formPost`, `indexBasedQueue`, `sonicSimilarity`, `transcoding`, `getPodcastEpisode`). Use `caps.supports(.songLyrics)` instead of the stringly-typed overload.
+
+- **`ServerCapabilities.extensionList`** — computed property that derives a `[OpenSubsonicExtension]` array from the extensions dictionary, matching the shape returned by `getOpenSubsonicExtensions()`.
+
+- **`ServerCapabilities.legacy()`** — factory that creates a non-OpenSubsonic capability snapshot with empty extensions, useful as a safe default when `fetchCapabilities()` has not been called.
+
+- **`ServerCapabilities` public init** — all five fields are now constructible from outside the module, enabling consumer-side mocking and testing.
+
+- **`loadCapabilities()`** — lazy capability accessor on `SwiftSonicClient`. Fetches from the server on first call; returns the cached value on all subsequent calls. `@discardableResult`.
+
+- **`refreshCapabilities()`** — forces a new `fetchCapabilities()` pass and updates the cached `serverCapabilities` property. Use after re-authentication or when you suspect the server configuration has changed. `@discardableResult`.
+
+- **`getLyricsBySongId(id:)`** — implements the OpenSubsonic `songLyrics` extension. Returns a `LyricsList` containing an array of `StructuredLyrics` sets, each with a language code, sync flag, optional display metadata, and an array of `Line` values (with optional millisecond `start` timestamps for synced lyrics).
+
+- **New model types** (`Lyrics.swift`):
+  - `LyricsList` — top-level container; `structuredLyrics` defaults to `[]` when absent from the response.
+  - `StructuredLyrics` — one language set; fields `lang`, `synced`, `line`, `displayArtist`, `displayTitle`, `offset`.
+  - `Line` — a single lyric line; `value` (String) + optional `start` (Int, milliseconds).
+
+- **`OpenSubsonicExtension` public init** — `init(name:versions:)` is now public.
+
+- **Public inits for all `SharedModels` types** — `ItemGenre`, `ReplayGain`, `ItemDate`, `DiscTitle`, `RecordLabel`, `ContributorArtist`, and `Contributor` all gain public memberwise initialisers with `nil` defaults on optional fields.
+
+- **OpenSubsonic fields on `Song`** — `mediaType: String?` and `displayComposer: String?` added to `Song` and its public init (both default to `nil`).
+
+- **OpenSubsonic fields on `AlbumID3`** — `explicitStatus: String?` and `version: String?` added to `AlbumID3` and its public init (both default to `nil`).
+
+- **Test count** — test suite grows from 296 to ~370 tests across new suites covering capabilities caching, `KnownExtension`, `getLyricsBySongId` decoding (synced, unsynced, multi-language, empty), and all new public inits.
+
+### Notes
+
+All changes are additive; no breaking changes from v0.6.x. The new `loadCapabilities()` / `refreshCapabilities()` methods complement the existing `fetchCapabilities()` + `serverCapabilities` property pair — choose whichever pattern suits your architecture.
+
+---
+
 ## [0.6.1] — 2026-04-27
 
 ### Added

README.md

@@ -98,16 +98,20 @@ let client = SwiftSonicClient(
 ### Checking server capabilities
 
 ```swift
-try await client.fetchCapabilities()
+// Lazy — fetches once, caches for all subsequent calls
+let caps = try await client.loadCapabilities()
+print("Server: \(caps.serverType ?? "unknown") \(caps.serverVersion ?? "")")
+print("OpenSubsonic: \(caps.isOpenSubsonic)")
 
-if let caps = client.serverCapabilities {
-    print("Server: \(caps.serverType ?? "unknown") \(caps.serverVersion ?? "")")
-    print("OpenSubsonic: \(caps.isOpenSubsonic)")
+// String overload
+if caps.supports("songLyrics") { … }
 
-    if caps.supports("songLyrics") {
-        // call OpenSubsonic-specific endpoints
-    }
-}
+// Typed KnownExtension overload (compile-time safe)
+if caps.supports(.songLyrics) { … }
+if caps.supports(.apiKeyAuthentication) { … }
+
+// Force a fresh fetch (e.g. after re-auth)
+let refreshed = try await client.refreshCapabilities()
 ```
 
 ### Browsing
@@ -306,7 +310,7 @@ let client = SwiftSonicClient(
 |---|---|
 | `ping` | `ping()` |
 | `getLicense` | `getLicense()` |
-| `getOpenSubsonicExtensions` | `getOpenSubsonicExtensions()` / `fetchCapabilities()` |
+| `getOpenSubsonicExtensions` | `getOpenSubsonicExtensions()` / `fetchCapabilities()` / `loadCapabilities()` / `refreshCapabilities()` |
 
 ### Browsing (ID3)
 | Endpoint | Swift API |
@@ -393,9 +397,30 @@ let client = SwiftSonicClient(
 | `addChatMessage` | `addChatMessage(_:)` |
 
 ### Lyrics
-| Endpoint | Swift API |
-|---|---|
-| `getLyrics` | `getLyrics(artist:title:)` |
+| Endpoint | Swift API | Notes |
+|---|---|---|
+| `getLyrics` | `getLyrics(artist:title:)` | Legacy Subsonic |
+| `getLyricsBySongId` | `getLyricsBySongId(id:)` | OpenSubsonic `songLyrics` extension |
+
+```swift
+// Legacy plain-text lyrics
+if let lyrics = try await client.getLyrics(artist: "Nine Inch Nails", title: "Hurt") {
+    print(lyrics.value ?? "")
+}
+
+// OpenSubsonic structured lyrics (synced + multi-language)
+let list = try await client.getLyricsBySongId(id: song.id)
+for set in list.structuredLyrics {
+    print("\(set.lang) synced=\(set.synced)")
+    for line in set.line {
+        if let ms = line.start {
+            print("[\(ms)ms] \(line.value)")
+        } else {
+            print(line.value)
+        }
+    }
+}
+```
 
 ### User management
 | Endpoint | Swift API |