fix(done): get issue ID from agent hook and detect integration branches (#411) (#453)

Branch names like "polecat/furiosa-mkb0vq9f" don't contain the actual
issue ID, causing gt done to incorrectly parse "furiosa-mkb0vq9f" as the
issue. This broke integration branch auto-detection since the wrong issue
was used for parent epic lookup.

Changes:
- After parsing branch name, check the agent's hook_bead field which
  contains the actual issue ID (e.g., "gt-845.1")
- Fix parseBranchName to not extract fake issue IDs from modern polecat branches
- Fix detectIntegrationBranch to traverse full parent chain (molecule → bug → epic)
- Include issue ID in polecat branch names when HookBead is set

Added tests covering:
- Agent hook returns correct issue ID
- Modern polecat branch format parsing
- Integration branch detection through parent chain

Fixes #411

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

internal/cmd/mq_test.go

@@ -68,6 +68,24 @@ func TestParseBranchName(t *testing.T) {
 			wantIssue:  "gt-abc.1",
 			wantWorker: "Worker",
 		},
+		{
+			name:       "polecat branch with issue and timestamp",
+			branch:     "polecat/furiosa/gt-jns7.1@mk123456",
+			wantIssue:  "gt-jns7.1",
+			wantWorker: "furiosa",
+		},
+		{
+			name:       "modern polecat branch (timestamp format)",
+			branch:     "polecat/furiosa-mkc36bb9",
+			wantIssue:  "", // Should NOT extract fake issue from worker-timestamp
+			wantWorker: "furiosa",
+		},
+		{
+			name:       "modern polecat branch with longer name",
+			branch:     "polecat/citadel-mk0vro62",
+			wantIssue:  "",
+			wantWorker: "citadel",
+		},
 		{
 			name:       "simple issue branch",
 			branch:     "gt-xyz",