Add federation worker and canonical handoffs

internal/herdr/herdr.go

@@ -160,6 +160,10 @@ type Session struct {
 	// its §6.1 handoff (HandoffFile) — avoids re-sending the same prompt
 	// every tick while Release keeps waiting for the file to appear.
 	HandoffRequested bool `json:"handoff_requested,omitempty"`
+	// HandoffReason is selected by the coordinator when it asks for the
+	// semantic report. The checkout worker, rather than the harness, copies
+	// it into the canonical handoff it seals at release time.
+	HandoffReason string `json:"handoff_reason,omitempty"`
 	// ConventionsHash is continuity.ConventionsHash of the project's shared
 	// *.md docs (AGENTS.md/CLAUDE.md/VOCAB.md) at the time this session was
 	// last notified of (or started with) their content — §6.3's staleness
@@ -455,10 +459,16 @@ func agentName(harness, taskID string) string {
 		id = "session"
 	}
 	name := prefix + "-" + id
-	if len(name) > 32 {
-		name = strings.TrimRight(name[:32], "-_")
+	if len(name) <= 32 {
+		return name
 	}
-	return name
+	// Keeping only the leading task-id characters made distinct long task
+	// IDs collide in herdr's machine-global name namespace. Reserve a stable
+	// digest suffix so truncation remains bounded *and* task-specific.
+	sum := sha256.Sum256([]byte(taskID))
+	const suffixLen = 8
+	keep := 32 - len(prefix) - 1 - 1 - suffixLen // prefix + "-" + stem + "-" + digest
+	return prefix + "-" + strings.TrimRight(id[:keep], "-_") + "-" + fmt.Sprintf("%x", sum[:])[:suffixLen]
 }
 
 // harnessStartArgs stays empty for Claude: --dangerously-skip-permissions