Implement find() wait and RECONNECT structure event (#24)

find() now waits for the target app to appear instead of failing
immediately. subscribeToStructure fires RECONNECT (2) when an app
reappears after being removed, distinguishing restarts from first-time
appearances.

Changes:
- find() waits indefinitely by default; { timeout: N } limits the wait;
  { timeout: 0 } preserves the old immediate-fail behavior
- find() works without prior root() call (triggers connection internally)
- close() is terminal: sets isClosed flag, rejects pending find() waiters,
  prevents reconnection after close
- RECONNECT constant (2) added alongside ADD (1) and REMOVE (0)
- Per-app lifecycle via announceApp/unannounceApp: each app is tracked
  independently, fixing the bug where one sibling disconnecting lost
  all sibling connections
- Subscription keepalive via inactivityResendInterval field
- Per-listener event dedup with composite keys and history wait window
- Value dedup via per-node timestamp tracking
- Exponential backoff with jitter for reconnection
- Stall detection: force reconnect after prolonged server silence
  with active subscriptions
- Direct mode sibling discovery uses server-pushed
  eStructureChangeResponse instead of client-side polling
- CDP_FORCE_DIRECT_MODE=1 env var to force direct mode on proxy-capable
  servers (for testing)
- Cache key fix: use join('.') instead of toString() for correct
  invalidateApp prefix matching on app structure changes
- Remove unused serviceId storage on proxy connections
- Fix instanceId serialization: pass through as-is instead of defaulting
  falsy values to 0
- appAddress() helper for DRY server address construction
- README updated with Structure Events section and find() options
- Version bump to 3.0.0 (breaking: find() default changed from
  immediate fail to indefinite wait)

CDP-6069

Author: stefanrammo

README.rst

@@ -38,6 +38,8 @@ Example
           root.subscribeToStructure((name, change) => {
             if (change === studio.api.structure.ADD)
               subscribeToApp(name);
+            if (change === studio.api.structure.RECONNECT)
+              console.log(`${name} restarted, subscriptions intact`);
           });
         }).catch(err => console.error("Connection failed:", err));
 
@@ -61,6 +63,41 @@ Benefits
 - Simplified firewall configuration - only one port needs to be opened
 - SSH port forwarding - forward a single port to access entire CDP system
 
+Structure Events
+----------------
+
+On the root node, ``subscribeToStructure`` tracks application lifecycle with three event types:
+
+- ``studio.api.structure.ADD`` (1) — An application appeared for the first time
+- ``studio.api.structure.REMOVE`` (0) — An application went offline
+- ``studio.api.structure.RECONNECT`` (2) — An application restarted (was seen before, went offline, came back)
+
+On other nodes, ADD and REMOVE fire when children are added or removed at runtime.
+RECONNECT only fires at the root level.
+
+When an app restarts, the client automatically restores value and event subscriptions,
+so user code does not need to re-subscribe. RECONNECT is informational — use it for
+logging or UI updates.
+
+    .. code:: javascript
+
+        client.root().then(root => {
+          root.subscribeToStructure((appName, change) => {
+            if (change === studio.api.structure.ADD) {
+              console.log(`New app online: ${appName}`);
+              client.find(appName + '.CPULoad').then(node => {
+                node.subscribeToValues(v => console.log(`[${appName}] CPULoad: ${v}`));
+              }).catch(err => console.error(`Failed to find ${appName}.CPULoad:`, err));
+            }
+            if (change === studio.api.structure.REMOVE) {
+              console.log(`App offline: ${appName}`);
+            }
+            if (change === studio.api.structure.RECONNECT) {
+              console.log(`App restarted: ${appName}, subscriptions intact`);
+            }
+          });
+        }).catch(err => console.error("Connection failed:", err));
+
 API
 ---
 
@@ -325,31 +362,46 @@ client.root()
           // use the system INode object to access connected structure.
         });
 
-client.find(path)
-^^^^^^^^^^^^^^^^^
+client.find(path, options)
+^^^^^^^^^^^^^^^^^^^^^^^^^
 
 - Arguments
 
-    path - Path of the object to look for.
+    path - Dot-separated path to target node (e.g. ``'App2.CPULoad'``).
+
+    options - Optional. Without this, find() waits indefinitely for the app to appear.
+    ``{ timeout: milliseconds }`` to limit wait time.
+    ``{ timeout: 0 }`` to fail immediately if the app is not available.
 
 - Returns
 
     Promise containing requested INode object when fulfilled.
 
-- Restriction
+- Behavior
 
-    The requested node must reside in the application client was connected to.
+    When no timeout option is provided, waits indefinitely for the target application to appear.
+    If the application is already available, resolves immediately. No prior ``root()`` call is needed — ``find()`` triggers
+    the connection internally.
 
-- Usage
+- Examples
 
-    The provided path must contain dot separated path to target node. **Root node is not considered part of the path.**
+    .. code:: javascript
 
-- Example
+        // Waits indefinitely for App2 to appear
+        client.find("App2.CPULoad").then(function (load) {
+          load.subscribeToValues(function (value) {
+            console.log("CPULoad:", value);
+          });
+        });
 
-    .. code:: javascript
+        // Wait up to 5 seconds
+        client.find("App2.CPULoad", { timeout: 5000 }).catch(function (err) {
+          console.log(err.message); // "App2 not found within 5000ms"
+        });
 
-        client.find("MyApp.CPULoad").then(function (load) {
-          // use the load object referring to CPULoad in MyApp
+        // Fail immediately if not available (old behavior)
+        client.find("App2.CPULoad", { timeout: 0 }).catch(function (err) {
+          console.log("Not available right now");
         });
 
 client.close()
@@ -604,8 +656,9 @@ node.subscribeToStructure(structureConsumer)
 
 - Usage
 
-    Subscribe to structure changes on this node. Each time child is added or removed from current node
-    structureConsumer function is called with the name of the node and change argument where ADD == 1 and REMOVE == 0.
+    Subscribe to structure changes on this node. Each time a child is added or removed,
+    structureConsumer is called with the child name and change (ADD == 1, REMOVE == 0).
+    On the root node, RECONNECT (2) fires when a previously-seen application restarts.
 
 node.unsubscribeFromStructure(structureConsumer)
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^