fix: tombstone/deletion overhaul for bd-4q8

- IsExpired(): Negative TTL means immediately expired (for --hard mode)
- IsExpired(): ClockSkewGrace only added for TTLs > 1 hour
- bd cleanup --hard: Use negative TTL to prune freshly created tombstones
- bd delete --hard: New flag to immediately prune tombstones from JSONL
- Import: Add early tombstone check before all phases to prevent resurrection

The early tombstone check prevents ghost issues from being created when
tombstones exist in the DB. However, a deeper git merge issue (bd-ncwo)
can still cause resurrection when remote's status:closed wins the merge.

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/types/types.go

@@ -98,7 +98,10 @@ func (i *Issue) IsTombstone() bool {
 
 // IsExpired returns true if the tombstone has exceeded its TTL.
 // Non-tombstone issues always return false.
-// ttl is the configured TTL duration; if zero, DefaultTombstoneTTL is used.
+// ttl is the configured TTL duration:
+//   - If zero, DefaultTombstoneTTL (30 days) is used
+//   - If negative, the tombstone is immediately expired (for --hard mode)
+//   - If positive, ClockSkewGrace is added only for TTLs > 1 hour
 func (i *Issue) IsExpired(ttl time.Duration) bool {
 	// Non-tombstones never expire
 	if !i.IsTombstone() {
@@ -110,13 +113,22 @@ func (i *Issue) IsExpired(ttl time.Duration) bool {
 		return false
 	}
 
+	// Negative TTL means "immediately expired" - for --hard mode (bd-4q8 fix)
+	if ttl < 0 {
+		return true
+	}
+
 	// Use default TTL if not specified
 	if ttl == 0 {
 		ttl = DefaultTombstoneTTL
 	}
 
-	// Add clock skew grace period to the TTL
-	effectiveTTL := ttl + ClockSkewGrace
+	// Only add clock skew grace period for normal TTLs (> 1 hour).
+	// For short TTLs (testing/development), skip grace period.
+	effectiveTTL := ttl
+	if ttl > ClockSkewGrace {
+		effectiveTTL = ttl + ClockSkewGrace
+	}
 
 	// Check if the tombstone has exceeded its TTL
 	expirationTime := i.DeletedAt.Add(effectiveTTL)

internal/types/types_test.go

@@ -756,6 +756,31 @@ func TestIsExpired(t *testing.T) {
 			ttl:     7 * 24 * time.Hour,
 			expired: false,
 		},
+		{
+			name: "negative TTL means immediately expired (bd-4q8 --hard mode)",
+			issue: Issue{
+				ID:        "test-14",
+				Title:     "(deleted)",
+				Status:    StatusTombstone,
+				Priority:  0,
+				IssueType: TypeTask,
+				DeletedAt: timePtr(now), // Just deleted NOW
+			},
+			ttl:     -1, // Negative TTL = immediate expiration
+			expired: true,
+		},
+		{
+			name: "non-tombstone never expires even with negative TTL",
+			issue: Issue{
+				ID:        "test-15",
+				Title:     "Open issue",
+				Status:    StatusOpen,
+				Priority:  0,
+				IssueType: TypeTask,
+			},
+			ttl:     -1,
+			expired: false,
+		},
 	}
 
 	for _, tt := range tests {