Make provider catalog refresh deadlines configurable (#3322)

* fix(providers): make catalog refresh deadlines configurable

Provider startup can legitimately exceed a fixed short timeout when catalog discovery has substantial initialization work. Give each provider refresh one configurable deadline covering availability and the complete catalog probe, and cancel named child operations before allowing retries so timed-out work cannot accumulate in the background.

* fix(opencode): abort catalog server acquisition

A provider refresh could expire while the helper server was still starting because acquisition only tracked the activity without observing its abort signal. Reject acquisition before transferring a server reference, while leaving the manager-owned startup reusable by the next caller.

* test(file-observer): allow native burst recovery

docs/custom-providers.md

@@ -2,7 +2,7 @@
 
 Paseo supports configuring custom agent providers through `config.json` (located at `$PASEO_HOME/config.json`, typically `~/.paseo/config.json`). You can extend built-in providers with different API backends, add ACP-compatible agents, set custom binaries, disable providers, and create multiple profiles for the same underlying provider.
 
-All provider configuration lives under `agents.providers` in config.json:
+Provider definitions live under `agents.providers` in config.json:
 
 ```json
 {
@@ -17,6 +17,20 @@ All provider configuration lives under `agents.providers` in config.json:
 
 Provider IDs must be lowercase alphanumeric with hyphens (`/^[a-z][a-z0-9-]*$/`).
 
+Each provider catalog refresh waits up to 60 seconds. If a provider loads many plugins or a large
+agent catalog during startup, raise the limit in milliseconds:
+
+```json
+{
+  "agents": {
+    "catalogRefreshTimeoutMs": 180000
+  }
+}
+```
+
+The limit applies independently to every provider refresh and covers availability plus the entire
+catalog probe. `PASEO_PROVIDER_REFRESH_TIMEOUT_MS` sets it when the config field is absent.
+
 ---
 
 ## Table of Contents