docs: refresh conformance and API docs

Author: nficano

CONFORMANCE.md

@@ -11,7 +11,7 @@ works" is decomposed into multiple binary rows.
 |---|---|---|
 | §4.1 WebSocket over `wss://` | Implemented | [arcp-runtime-jetty/src/main/java/dev/arcp/runtime/jetty/ArcpJettyServer.java:18](arcp-runtime-jetty/src/main/java/dev/arcp/runtime/jetty/ArcpJettyServer.java#L18) (server) + [arcp-client/src/main/java/dev/arcp/client/WebSocketTransport.java:29](arcp-client/src/main/java/dev/arcp/client/WebSocketTransport.java#L29) (client) |
 | §4.1 JSON text frames | Implemented | [arcp-runtime-jetty/src/main/java/dev/arcp/runtime/jetty/WebSocketJsonTransport.java](arcp-runtime-jetty/src/main/java/dev/arcp/runtime/jetty/WebSocketJsonTransport.java) |
-| §4.2 stdio newline-delimited JSON | Deferred | Not in 1.0.0; covered by `MemoryTransport` for in-process scenarios. |
+| §4.2 stdio newline-delimited JSON | Implemented | [arcp-core/src/main/java/dev/arcp/core/transport/StdioTransport.java](arcp-core/src/main/java/dev/arcp/core/transport/StdioTransport.java) |
 | §4.3 Alternate transports MAY exist | Implemented | [arcp-core/src/main/java/dev/arcp/core/transport/MemoryTransport.java](arcp-core/src/main/java/dev/arcp/core/transport/MemoryTransport.java) implements the `Transport` SPI |
 
 ## §5. Wire Format
@@ -20,7 +20,7 @@ works" is decomposed into multiple binary rows.
 |---|---|---|
 | §5.1 Envelope shape (`arcp`, `id`, `type`, `payload`, ...) | Implemented | [arcp-core/src/main/java/dev/arcp/core/wire/Envelope.java:22](arcp-core/src/main/java/dev/arcp/core/wire/Envelope.java#L22) |
 | §5.1 Unknown top-level fields ignored | Implemented | [arcp-core/src/main/java/dev/arcp/core/wire/ArcpMapper.java](arcp-core/src/main/java/dev/arcp/core/wire/ArcpMapper.java) sets `FAIL_ON_UNKNOWN_PROPERTIES=false` |
-| §5.1 `arcp` version string `"1"` | Implemented | [arcp-core/src/main/java/dev/arcp/core/wire/Envelope.java:31](arcp-core/src/main/java/dev/arcp/core/wire/Envelope.java#L31) |
+| §5.1 `arcp` version string `"1.1"` | Implemented | [arcp-core/src/main/java/dev/arcp/core/wire/Envelope.java:31](arcp-core/src/main/java/dev/arcp/core/wire/Envelope.java#L31) |
 
 ## §6. Sessions
 

arcp-core/src/main/java/dev/arcp/core/capabilities/Capabilities.java

@@ -12,7 +12,7 @@
 
 /**
  * Client/runtime capability advertisement carried on session.hello and session.welcome. Unknown
- * feature strings are preserved on the wire as ignored but round-trip-safe.
+ * feature strings are ignored and dropped during decoding.
  */
 public record Capabilities(
     List<String> encodings, Set<Feature> features, @Nullable List<AgentDescriptor> agents) {

arcp-core/src/main/java/dev/arcp/core/wire/ArcpMapper.java

@@ -33,7 +33,13 @@ public static ObjectMapper create() {
 
   private static final ObjectMapper SHARED = create();
 
-  /** Shared, immutable mapper for hot-path use. */
+  /**
+   * Shared mapper for hot-path use.
+   *
+   * Treat this instance as read-only. Reconfiguring the shared mapper can
+   * affect unrelated callers because the same ObjectMapper is reused across
+   * the SDK.
+   */
   public static ObjectMapper shared() {
     return SHARED;
   }

arcp-runtime/src/main/java/dev/arcp/runtime/lease/BudgetCounters.java

@@ -53,7 +53,11 @@ public void decrement(String currency, BigDecimal amount) {
     ref.updateAndGet(b -> b.subtract(amount));
   }
 
-  /** Returns null if all budgets are positive; otherwise throws. */
+  /**
+   * Returns normally if all budgets remain positive.
+   *
+   * @throws BudgetExhaustedException if any counter reaches zero or below
+   */
   public void ensureAllPositive() throws BudgetExhaustedException {
     for (var e : counters.entrySet()) {
       if (e.getValue().get().signum() <= 0) {