refactor: move act under internal

The runner is an application, not a library. `act/model` and
`act/exprparser` were the last packages anything outside this repository
consumed and they now live in actionslib, so nothing needs the rest of
`act` to be importable, and keeping it importable invites the coupling
that was just removed.

Import paths only, the files are unchanged.

Assisted-by: Codet:GPT-5.1-Codex

internal/act/artifactcache/model.go

@@ -0,0 +1,39 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// Copyright 2023 The nektos/act Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package artifactcache
+
+type Request struct {
+	Key     string `json:"key" `
+	Version string `json:"version"`
+	Size    int64  `json:"cacheSize"`
+}
+
+func (c *Request) ToCache() *Cache {
+	if c == nil {
+		return nil
+	}
+	ret := &Cache{
+		Key:     c.Key,
+		Version: c.Version,
+		Size:    c.Size,
+	}
+	if c.Size == 0 {
+		// So the request comes from old versions of actions, like `actions/cache@v2`.
+		// It doesn't send cache size. Set it to -1 to indicate that.
+		ret.Size = -1
+	}
+	return ret
+}
+
+type Cache struct {
+	ID        uint64 `json:"id" boltholdKey:"ID"`
+	Repo      string `json:"repo" boltholdIndex:"Repo"`
+	Key       string `json:"key" boltholdIndex:"Key"`
+	Version   string `json:"version" boltholdIndex:"Version"`
+	Size      int64  `json:"cacheSize"`
+	Complete  bool   `json:"complete" boltholdIndex:"Complete"`
+	UsedAt    int64  `json:"usedAt" boltholdIndex:"UsedAt"`
+	CreatedAt int64  `json:"createdAt" boltholdIndex:"CreatedAt"`
+}