feat(pulls): add resolve, unresolve and review-comments subcommands (#948)

## Summary

- Add `tea pulls review-comments <pull-index>` subcommand to list PR review comments with configurable fields (supports table/json/csv/yaml output)
- Add `tea pulls resolve <comment-id>` subcommand to mark a review comment as resolved
- Add `tea pulls unresolve <comment-id>` subcommand to unmark a review comment as resolved
- Follow existing approve/reject pattern with shared `runResolveComment` helper in `review_helpers.go`

## Usage

```bash
# List review comments for PR #42
tea pulls review-comments 42

# Resolve comment #789
tea pulls resolve 789

# Unresolve comment #789
tea pulls unresolve 789

# Custom output fields
tea pulls review-comments 42 --fields id,path,body,resolver --output json
```

## New Files

| File | Description |
|------|-------------|
| `cmd/pulls/review_comments.go` | `review-comments` subcommand |
| `cmd/pulls/resolve.go` | `resolve` subcommand |
| `cmd/pulls/unresolve.go` | `unresolve` subcommand |
| `modules/task/pull_review_comment.go` | Task layer: list, resolve, unresolve via SDK |
| `modules/print/pull_review_comment.go` | Print formatting with `printable` interface |

## Modified Files

| File | Description |
|------|-------------|
| `cmd/pulls.go` | Register 3 new commands |
| `cmd/pulls/review_helpers.go` | Add shared `runResolveComment` helper |

## Test Plan

- [x] `go build ./...` passes
- [x] `go vet ./...` passes
- [x] `tea pulls review-comments <PR-index>` lists comments with IDs
- [x] `tea pulls resolve <comment-id>` resolves successfully
- [x] `tea pulls unresolve <comment-id>` unresolves successfully
- [x] `--output json` produces valid JSON output

Reviewed-on: https://gitea.com/gitea/tea/pulls/948
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: Bo-Yi Wu <appleboy.tw@gmail.com>
Co-committed-by: Bo-Yi Wu <appleboy.tw@gmail.com>

cmd/pulls/unresolve.go

@@ -0,0 +1,30 @@
+// Copyright 2026 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package pulls
+
+import (
+	stdctx "context"
+
+	"code.gitea.io/tea/cmd/flags"
+	"code.gitea.io/tea/modules/context"
+	"code.gitea.io/tea/modules/task"
+
+	"github.com/urfave/cli/v3"
+)
+
+// CmdPullsUnresolve unresolves a review comment on a pull request
+var CmdPullsUnresolve = cli.Command{
+	Name:        "unresolve",
+	Usage:       "Unresolve a review comment on a pull request",
+	Description: "Unresolve a review comment on a pull request",
+	ArgsUsage:   "<comment id>",
+	Action: func(_ stdctx.Context, cmd *cli.Command) error {
+		ctx, err := context.InitCommand(cmd)
+		if err != nil {
+			return err
+		}
+		return runResolveComment(ctx, task.UnresolvePullReviewComment)
+	},
+	Flags: flags.AllDefaultFlags,
+}