aitools: raise the plugin probe timeout from 5s to 20s

`databricks aitools install` runs `<agent> plugin --help` to check that the agent's CLI can install plugins. Agent CLIs are large Node/Rust binaries, and a cold start (first run, antivirus scan, slow container disk) can take several seconds. When the probe times out, the agent is reported as unavailable.

```diff
 // libs/aitools/installer/plugin.go
-pluginProbeTimeout = 5 * time.Second
+pluginProbeTimeout = 20 * time.Second
```

The same constant also bounds `<agent> plugin marketplace list`. Changelog fragment: `.nextchanges/cli/aitools-plugin-probe-timeout.md`.

Co-authored-by: Isaac <no-reply@databricks.com>

Author: anton-107

.nextchanges/cli/aitools-plugin-probe-timeout.md

@@ -0,0 +1 @@
+* `databricks aitools install` and `databricks aitools update` now wait up to 20 seconds instead of 5 for a coding agent's CLI to answer the plugin capability check, so a slow first start is less likely to report the agent as unavailable. ([#7472](https://github.com/databricks/cli/pull/7472))

libs/aitools/agents/detect.go

@@ -16,8 +16,9 @@ import (
 var lookPath = exec.LookPath
 
 // pluginProbeTimeout bounds the `<agent> plugin --help` capability probe so a
-// hung agent CLI cannot stall install.
-const pluginProbeTimeout = 5 * time.Second
+// hung agent CLI cannot stall install. It matches the probe timeout in
+// libs/aitools/installer, which leaves headroom for a slow agent CLI cold start.
+const pluginProbeTimeout = 20 * time.Second
 
 // DisplayState describes how an agent should be presented in the install
 // picker. It combines the two cheap presence signals (binary on PATH and

libs/aitools/installer/plugin.go

@@ -20,7 +20,13 @@ var lookPath = exec.LookPath
 
 const (
 	// pluginProbeTimeout bounds the `<agent> plugin --help` capability check.
-	pluginProbeTimeout = 5 * time.Second
+	// Agent CLIs are large Node/Rust binaries whose cold start (first run,
+	// antivirus scan, slow container disk) can take several seconds, and a probe
+	// that times out reports the agent as unavailable, so leave headroom.
+	// It also bounds `<agent> plugin marketplace list` in marketplaceRegistered,
+	// where a timeout means the marketplace is assumed already registered, so
+	// install does not record it and uninstall leaves it registered.
+	pluginProbeTimeout = 20 * time.Second
 	// pluginCmdTimeout bounds an install/update/uninstall command, which may
 	// clone the marketplace repo, so it gets more headroom than the probe.
 	pluginCmdTimeout = 60 * time.Second