fix(worker): preview_merge braucht einen runVerify-Parameter wie preview_merge_set

preview_merge baute bisher immer, sobald die Liste ein Verify-Kommando
konfiguriert hatte -- anders als das Geschwister-Tool preview_merge_set,
dessen runVerify-Parameter per Default false ist. Ein einzelnes preview_merge
im Merge-Helper-Recheck stiess dadurch einen ungewollten Scratch-Build an.

runVerify (Default false) jetzt symmetrisch bei preview_merge ergaenzt,
Description-Text und die Merge-Helper-Prompt-Doku angepasst.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/ClaudeDo.Data/PromptFiles.cs

@@ -523,7 +523,7 @@ public static class PromptFiles
            - Clean merge → mergeStatus "merged_verify_pending" (expected: the task deliberately stays WaitingForReview until verify_merges passes) or "merged" (list has no verify command; the task is Done). Either way, move on.
            - Conflict (markers left in the working tree, repoPath returned) → resolve it below.
 
-        After each merge, main has moved — a clean preview_merge_set result from before this merge is now stale for the remaining tasks. If you are unsure whether an earlier overlap warning still matters, call preview_merge for the next task again before merging it.
+        After each merge, main has moved — a clean preview_merge_set result from before this merge is now stale for the remaining tasks. If you are unsure whether an earlier overlap warning still matters, call preview_merge for the next task again before merging it (default runVerify=false — this is just a conflict recheck, not a build; the verify command still runs once via verify_merges after the last merge).
 
         Every branch in this run forked from the same base, so conflicts between them are the NORMAL case, not a failure. Resolve them and keep going; do not abandon the run because a merge conflicted.
 

src/ClaudeDo.Worker/External/MergeMcpTools.cs

@@ -446,26 +446,30 @@ public sealed class MergeMcpTools
         "untracked, in the target working directory — merge-tree can't see the working tree at all, so this is the " +
         "only way to catch it before a real merge either refuses or, if that path became tracked in the meantime, " +
         "silently overwrites it); behind counts commits on targetBranch not yet on this branch, which flags a stale " +
-        "branch even when the preview is clean. If the list has a verify command configured, a clean preview is " +
-        "additionally built/tested in a scratch worktree (still without touching the real working tree) — " +
-        "verifyExitCode 0 means it built clean, non-zero or -1 (timeout/failed to start) means it doesn't, with the " +
-        "tail of its output in verifyOutputTail; verifyExitCode stays null when no verify command is configured. " +
-        "isEmpty=true means the task's review range contributed nothing; check that flag rather than reading a " +
-        "small changedFileCount as empty. staleFiles lists files this branch touches that the target branch ALSO " +
-        "changed since this branch's fork point — a more honest staleness signal than `behind` alone, since a " +
-        "branch can be far behind yet touch nothing the target changed, or barely behind yet collide on the one " +
-        "file that matters (always empty for a worktree-less handler task, which has no fork point). Throws if the " +
-        "task has neither an active worktree nor a handler commit range, or the list's working directory is missing " +
-        "from disk." + McpToolDocs.ProgressHint)]
+        "branch even when the preview is clean. runVerify=false (default) never builds. runVerify=true additionally " +
+        "builds/tests a clean preview in a scratch worktree (still without touching the real working tree), if the " +
+        "list has a verify command configured — verifyExitCode 0 means it built clean, non-zero or -1 " +
+        "(timeout/failed to start) means it doesn't, with the tail of its output in verifyOutputTail; " +
+        "verifyExitCode/verifyDurationMs/verifyOutputTail stay null without runVerify=true or without a configured " +
+        "verify command. isEmpty=true means the task's review range contributed nothing; check that flag rather " +
+        "than reading a small changedFileCount as empty. staleFiles lists files this branch touches that the " +
+        "target branch ALSO changed since this branch's fork point — a more honest staleness signal than `behind` " +
+        "alone, since a branch can be far behind yet touch nothing the target changed, or barely behind yet " +
+        "collide on the one file that matters (always empty for a worktree-less handler task, which has no fork " +
+        "point). Throws if the task has neither an active worktree nor a handler commit range, or the list's " +
+        "working directory is missing from disk." + McpToolDocs.ProgressHint)]
     public async Task<MergePreviewToolDto> PreviewMerge(
         string taskId,
         [Description("Branch to preview against; defaults to the repo's current branch.")]
         string? targetBranch = null,
+        [Description("true: also run the verify command (if configured), building in a scratch worktree. " +
+                     "false (default): no build.")]
+        bool runVerify = false,
         CancellationToken cancellationToken = default,
         IProgress<ProgressNotificationValue>? progress = null)
     {
         taskId = await TaskIdResolver.ResolveAsync(_tasks, taskId, cancellationToken);
-        var (preview, behind, _, isEmpty, staleFiles, _, _) = await PreviewMergeCoreAsync(taskId, targetBranch, runVerify: true, cancellationToken, progress);
+        var (preview, behind, _, isEmpty, staleFiles, _, _) = await PreviewMergeCoreAsync(taskId, targetBranch, runVerify, cancellationToken, progress);
         return new MergePreviewToolDto(preview.Status, preview.ConflictFiles, preview.ChangedFileCount, behind, isEmpty,
             preview.VerifyExitCode, preview.VerifyDurationMs, preview.VerifyOutputTail, staleFiles);
     }