Nodes show their engines' versions and GPUs' capability; a profile can ask for an engine version

NodeView carries engine_versions and compute_capabilities; ctl nodes shows
llamacpp b10991 and 6000-24g (7.5). A profile's engine_version restricts it
to nodes whose engine version starts with it, and explain-placement says
which version a node has, or which engines it has when it lacks the one
asked for.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

docs/reference.md

@@ -203,6 +203,7 @@ rather than repeated.
 | `files` | `[]OriginFile` | [PreviousOrigin](#previousorigin) |
 | `name` | `string` | [Profile](#profile) |
 | `engine` | `string` | [Profile](#profile) |
+| `engine_version` | `string` | [Profile](#profile) |
 | `gpu_class` | `string` | [Profile](#profile) |
 | `tp` | `int` | [Profile](#profile) |
 | `pp` | `int` | [Profile](#profile) |
@@ -1756,6 +1757,14 @@ before affinity is abandoned.
 
 `string`
 
+### `engine_version`
+
+`string`
+
+EngineVersion restricts the profile to nodes whose installed engine's
+version starts with it: "0.11" takes vLLM 0.11.0 and 0.11.1, not
+0.10.2. Empty takes whatever version the node has.
+
 ### `gpu_class`
 
 `string`