Fix models support with compose include

[doringeman]

Fixes 3 related issues preventing models from working with the include directive:

• Missing merge logic for models in override package.
• Short syntax validation failed (models: [llama] → {llama: null} violates schema).
• Models weren't being imported from included files (missing from importResources).

E.g.,
Fixes running docker-compose up with the root docker-compose.yml in docker/hello-genai#15.

Before this PR:

$ docker compose up
validating /Users/doringeman/workspace/hello-genai/docker-compose.yml: services.go-genai.models.llama must be a mapping

After the second commit (run go mod edit -replace=github.com/compose-spec/compose-go/v2=github.com/doringeman/compose-go/v2@80d4df69626c3c3ab08f5c3af0870de5900aecde && go mod tidy && make install in https://github.com/docker/compose):

$ docker compose up
service "rust-genai" refers to undefined model llama: invalid compose project

After the third commit (run go mod edit -replace=github.com/compose-spec/compose-go/v2=github.com/doringeman/compose-go/v2@95abc2eef4c7b7d1278a34c2e548ec47a216acc9 && go mod tidy && make install in https://github.com/docker/compose):

$ docker compose up
[+] Running 4/5
 ⠙ llama Configuring                                                                                                0.1s
 ✔ Container hello-genai-rust-genai-1    Created                                                                    0.1s
 ✔ Container hello-genai-node-genai-1    Created                                                                    0.1s
 ✔ Container hello-genai-python-genai-1  Created                                                                    0.1s
 ✔ Container hello-genai-go-genai-1      Created                                                                    0.1s
Attaching to go-genai-1, node-genai-1, python-genai-1, rust-genai-1

[ndeloof]

Changes to transformStringSliceToMap are not required, this same mechanism is used in many other places without any issue.

[ndeloof]

This requires an update on the compose-spec documentation to make it clear runtime_flags won't be appended
see https://github.com/compose-spec/compose-spec/blob/main/13-merge.md#exceptions

[ndeloof]

IMHO you don't need such a rule, for the use-case to fully redefine a model one would rely on !override

[ndeloof]

this should not be necessary, as next lines merge equivalent mapping syntax

[doringeman]

You mean to remove the comment only?

[ndeloof]

no, I mean this all block. Mutating into mapping format then merge is the right way, and should not require any extra processing - we do the same for the many other comparable structs

[doringeman]

Changes to transformStringSliceToMap are not required, this same mechanism is used in many other places without any issue.

In this case I'd need to add {"type": "null"} for models in compose-spec.json, right? This is why I changed transformStringSliceToMap.

diff --git a/schema/compose-spec.json b/schema/compose-spec.json
index 5db97d0..047a6b4 100644
--- a/schema/compose-spec.json
+++ b/schema/compose-spec.json
@@ -546,7 +546,8 @@
                   "patternProperties": {"^x-": {}}
                 }
               }
-            }
+            },
+            {"type": "null"}
           ],
           "description": "AI Models to use, referencing entries under the top-level models key."
         },

[ndeloof]

In this case I'd need to add {"type": "null"} for models in compose-spec.json, right?

I don't think so. See networks for a comparable struct. Can be set either as a string array or a mapping