feat(sync): auto-push after merge with safety check (bd-7ch)

Add auto-push functionality to PullFromSyncBranch for true one-command sync:
- After successful content merge, auto-push to remote by default
- Safety check: warn (but dont block) if >50% issues vanished AND >5 existed
- Vanished = removed from JSONL entirely, NOT status=closed

Changes:
- Add push parameter to PullFromSyncBranch function
- Add Pushed field to PullResult struct
- Add countIssuesInContent helper for safety check
- Add test for countIssuesInContent function

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

cmd/bd/sync.go

@@ -378,7 +378,7 @@ Use --merge to merge the sync branch back to main branch.`,
 				if useSyncBranch {
 					// Pull from sync branch via worktree (bd-e3w)
 					fmt.Printf("→ Pulling from sync branch '%s'...\n", syncBranchName)
-					pullResult, err := syncbranch.PullFromSyncBranch(ctx, repoRoot, syncBranchName, jsonlPath)
+					pullResult, err := syncbranch.PullFromSyncBranch(ctx, repoRoot, syncBranchName, jsonlPath, !noPush)
 					if err != nil {
 						fmt.Fprintf(os.Stderr, "Error pulling from sync branch: %v\n", err)
 						os.Exit(1)
@@ -387,6 +387,11 @@ Use --merge to merge the sync branch back to main branch.`,
 						if pullResult.Merged {
 							// bd-3s8 fix: divergent histories were merged at content level
 							fmt.Printf("✓ Merged divergent histories from %s\n", syncBranchName)
+							// bd-7ch: auto-push after merge
+							if pullResult.Pushed {
+								fmt.Printf("✓ Pushed merged changes to %s\n", syncBranchName)
+								pushedViaSyncBranch = true
+							}
 						} else if pullResult.FastForwarded {
 							fmt.Printf("✓ Fast-forwarded from %s\n", syncBranchName)
 						} else {

internal/syncbranch/worktree.go

@@ -29,6 +29,7 @@ type PullResult struct {
 	JSONLPath     string // Path to the synced JSONL in main repo
 	Merged        bool   // True if divergent histories were merged
 	FastForwarded bool   // True if fast-forward was possible
+	Pushed        bool   // True if changes were pushed after merge (bd-7ch)
 }
 
 // CommitToSyncBranch commits JSONL changes to the sync branch using a git worktree.
@@ -182,6 +183,10 @@ func preemptiveFetchAndFastForward(ctx context.Context, worktreePath, branch, re
 //  5. Reset to remote's history (adopt remote commit graph)
 //  6. Commit merged content on top
 //
+// IMPORTANT (bd-7ch): After successful content merge, auto-pushes to remote by default.
+// Includes safety check: warns (but doesn't block) if >50% issues vanished AND >5 existed.
+// "Vanished" means removed from issues.jsonl entirely, NOT status=closed.
+//
 // This ensures sync never fails due to git merge conflicts, as we handle merging at the
 // JSONL content level where we have semantic understanding of the data.
 //
@@ -190,9 +195,10 @@ func preemptiveFetchAndFastForward(ctx context.Context, worktreePath, branch, re
 //   - repoRoot: Path to the git repository root
 //   - syncBranch: Name of the sync branch (e.g., "beads-sync")
 //   - jsonlPath: Absolute path to the JSONL file in the main repo
+//   - push: If true, push to remote after merge (bd-7ch)
 //
 // Returns PullResult with details about what was done, or error if failed.
-func PullFromSyncBranch(ctx context.Context, repoRoot, syncBranch, jsonlPath string) (*PullResult, error) {
+func PullFromSyncBranch(ctx context.Context, repoRoot, syncBranch, jsonlPath string, push bool) (*PullResult, error) {
 	result := &PullResult{
 		Branch:    syncBranch,
 		JSONLPath: jsonlPath,
@@ -271,6 +277,9 @@ func PullFromSyncBranch(ctx context.Context, repoRoot, syncBranch, jsonlPath str
 	// 3. Reset to remote's commit history
 	// 4. Commit merged content on top
 
+	// bd-7ch: Extract local content before merge for safety check
+	localContent, _ := extractJSONLFromCommit(ctx, worktreePath, "HEAD", jsonlRelPath)
+
 	mergedContent, err := performContentMerge(ctx, worktreePath, syncBranch, remote, jsonlRelPath)
 	if err != nil {
 		return nil, fmt.Errorf("content merge failed: %w", err)
@@ -330,6 +339,31 @@ func PullFromSyncBranch(ctx context.Context, repoRoot, syncBranch, jsonlPath str
 		return nil, err
 	}
 
+	// bd-7ch: Auto-push after successful content merge
+	if push && hasChanges {
+		// Safety check: count issues before and after merge to detect mass deletion
+		localCount := countIssuesInContent(localContent)
+		mergedCount := countIssuesInContent(mergedContent)
+
+		// Warn if >50% issues vanished AND >5 existed before
+		// "Vanished" = removed from JSONL entirely (not status=closed)
+		if localCount > 5 && mergedCount < localCount {
+			vanishedPercent := float64(localCount-mergedCount) / float64(localCount) * 100
+			if vanishedPercent > 50 {
+				fmt.Fprintf(os.Stderr, "⚠️  Warning: %.0f%% of issues vanished during merge (%d → %d issues)\n",
+					vanishedPercent, localCount, mergedCount)
+				fmt.Fprintf(os.Stderr, "   This may indicate accidental mass deletion. Pushing anyway.\n")
+				fmt.Fprintf(os.Stderr, "   If this was unintended, use 'git reflog' on the sync branch to recover.\n")
+			}
+		}
+
+		// Push regardless of safety check (don't block happy path)
+		if err := pushFromWorktree(ctx, worktreePath, syncBranch); err != nil {
+			return nil, fmt.Errorf("failed to push after merge: %w", err)
+		}
+		result.Pushed = true
+	}
+
 	return result, nil
 }
 
@@ -636,6 +670,21 @@ func GetRepoRoot(ctx context.Context) (string, error) {
 	return strings.TrimSpace(string(output)), nil
 }
 
+// countIssuesInContent counts the number of non-empty lines in JSONL content.
+// Each non-empty line represents one issue. Used for safety checks (bd-7ch).
+func countIssuesInContent(content []byte) int {
+	if len(content) == 0 {
+		return 0
+	}
+	count := 0
+	for _, line := range strings.Split(string(content), "\n") {
+		if strings.TrimSpace(line) != "" {
+			count++
+		}
+	}
+	return count
+}
+
 // HasGitRemote checks if any git remote exists
 func HasGitRemote(ctx context.Context) bool {
 	cmd := exec.CommandContext(ctx, "git", "remote")

internal/syncbranch/worktree_divergence_test.go

@@ -458,3 +458,52 @@ func writeFile(t *testing.T, path, content string) {
 		t.Fatalf("Failed to write file %s: %v", path, err)
 	}
 }
+
+// TestCountIssuesInContent tests the issue counting helper function (bd-7ch)
+func TestCountIssuesInContent(t *testing.T) {
+	tests := []struct {
+		name    string
+		content []byte
+		want    int
+	}{
+		{
+			name:    "empty content",
+			content: []byte{},
+			want:    0,
+		},
+		{
+			name:    "nil content",
+			content: nil,
+			want:    0,
+		},
+		{
+			name:    "single issue",
+			content: []byte(`{"id":"test-1"}`),
+			want:    1,
+		},
+		{
+			name:    "multiple issues",
+			content: []byte(`{"id":"test-1"}` + "\n" + `{"id":"test-2"}` + "\n" + `{"id":"test-3"}`),
+			want:    3,
+		},
+		{
+			name:    "trailing newline",
+			content: []byte(`{"id":"test-1"}` + "\n" + `{"id":"test-2"}` + "\n"),
+			want:    2,
+		},
+		{
+			name:    "empty lines ignored",
+			content: []byte(`{"id":"test-1"}` + "\n" + "\n" + `{"id":"test-2"}` + "\n" + "   " + "\n"),
+			want:    2,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := countIssuesInContent(tt.content)
+			if got != tt.want {
+				t.Errorf("countIssuesInContent() = %d, want %d", got, tt.want)
+			}
+		})
+	}
+}