feat(tools): repo_tree, repo_topics_update, file_read dir fix (#14, #15, #18)

repo_tree: GET /git/trees/{ref}?recursive=1 — full recursive file tree
repo_topics_update: PUT /repos/{owner}/{repo}/topics — replace topic list
file_read: detect array response and return descriptive error for dir paths

internal/tools/repo_tree.go

@@ -0,0 +1,56 @@
+package tools
+
+import (
+	"context"
+	"encoding/json"
+
+	"gitea.d-ma.be/mathias/gitea-mcp/internal/allowlist"
+	"gitea.d-ma.be/mathias/gitea-mcp/internal/gitea"
+	"gitea.d-ma.be/mathias/gitea-mcp/internal/registry"
+)
+
+type RepoTree struct {
+	c *gitea.Client
+	a *allowlist.Allowlist
+}
+
+func NewRepoTree(c *gitea.Client, a *allowlist.Allowlist) *RepoTree {
+	return &RepoTree{c: c, a: a}
+}
+
+func (t *RepoTree) Descriptor() registry.ToolDescriptor {
+	return registry.ToolDescriptor{
+		Name:        "repo_tree",
+		Description: "Get the full recursive file tree for a repo ref (branch, tag, or SHA).",
+		InputSchema: json.RawMessage(`{
+			"type":"object",
+			"properties":{
+				"owner":{"type":"string"},
+				"name":{"type":"string"},
+				"ref":{"type":"string","description":"Branch, tag, or commit SHA."}
+			},
+			"required":["owner","name","ref"]
+		}`),
+	}
+}
+
+type repoTreeArgs struct {
+	Owner string `json:"owner"`
+	Name  string `json:"name"`
+	Ref   string `json:"ref"`
+}
+
+func (t *RepoTree) Call(ctx context.Context, raw json.RawMessage) (json.RawMessage, error) {
+	var args repoTreeArgs
+	if err := parseArgs(raw, &args); err != nil {
+		return nil, err
+	}
+	if err := t.a.Check(args.Owner); err != nil {
+		return nil, err
+	}
+	tree, err := t.c.GetTree(ctx, args.Owner, args.Name, args.Ref, true)
+	if err != nil {
+		return nil, err
+	}
+	return textOK(tree)
+}