feat(addons): GitHub add-on skeleton and read tools

Add the github add-on: manifest with a credential slot, a read-only
tool set (code search, files, trees, issues, pull requests and diffs)
with size caps and untrusted-content framing, rate-limit mapping, a
connector route that checks the token, and a fake GitHub API for tests.

Assisted-by: Claude:claude-sonnet-5-5 [go]

addons/github/cmd/github/main.go

@@ -0,0 +1,35 @@
+// SPDX-License-Identifier: MIT
+
+// Command github is the executable of the GitHub add-on. It reads repositories
+// for the chats and the agents with a token that the host keeps for the person
+// and hands over with each call. The add-on stores no token and writes nothing
+// to GitHub.
+package main
+
+import (
+	"context"
+	"os"
+
+	"github.com/mudler/LocalAI/addons/github/internal/ghapi"
+	"github.com/mudler/LocalAI/addons/github/internal/platform"
+	"github.com/mudler/LocalAI/addons/github/internal/tools"
+	"github.com/mudler/LocalAI/addons/internal/connector"
+	"github.com/mudler/LocalAI/addons/internal/protocol"
+	"github.com/mudler/LocalAI/pkg/addons/contract"
+)
+
+type runtime struct {
+	*tools.Runtime
+	platform platform.Platform
+}
+
+func (r runtime) Connector(ctx context.Context, req contract.ConnectorRequest) (contract.ConnectorResponse, error) {
+	return connector.Serve(ctx, r.platform, req)
+}
+
+func main() {
+	os.Exit(protocol.Run(os.Args, func(protocol.Startup) contract.Runtime {
+		api := ghapi.New()
+		return runtime{Runtime: tools.New(api), platform: platform.Platform{API: api}}
+	}))
+}