feat: add issue_list_comments tool (closes #32)

Lists all comments on an issue or PR via GET /api/v1/repos/{owner}/{repo}/issues/{index}/comments.
Read-only, allowlist-gated. Extended IssueComment struct with user/timestamps populated by the list endpoint.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

internal/tools/issue_list_comments.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 IssueListComments struct {
+	c *gitea.Client
+	a *allowlist.Allowlist
+}
+
+func NewIssueListComments(c *gitea.Client, a *allowlist.Allowlist) *IssueListComments {
+	return &IssueListComments{c: c, a: a}
+}
+
+func (t *IssueListComments) Descriptor() registry.ToolDescriptor {
+	return registry.ToolDescriptor{
+		Name:        "issue_list_comments",
+		Description: "List all comments on an issue or pull request. Returns id, body, author, html_url, and timestamps for each comment.",
+		InputSchema: json.RawMessage(`{
+			"type":"object",
+			"properties":{
+				"owner":{"type":"string"},
+				"name":{"type":"string"},
+				"number":{"type":"integer","minimum":1}
+			},
+			"required":["owner","name","number"]
+		}`),
+	}
+}
+
+type issueListCommentsArgs struct {
+	Owner  string `json:"owner"`
+	Name   string `json:"name"`
+	Number int    `json:"number"`
+}
+
+func (t *IssueListComments) Call(ctx context.Context, raw json.RawMessage) (json.RawMessage, error) {
+	var args issueListCommentsArgs
+	if err := parseArgs(raw, &args); err != nil {
+		return nil, err
+	}
+	if err := t.a.Check(args.Owner); err != nil {
+		return nil, err
+	}
+	comments, err := t.c.ListIssueComments(ctx, args.Owner, args.Name, args.Number)
+	if err != nil {
+		return nil, err
+	}
+	return textOK(comments)
+}