chore: strip remaining pre-fork version references

Second pass — removes chat-switchboard version numbers from config
field docs, section headers, file headers, and test comments. These
were pre-fork version tags that don't apply to switchboard-core.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

server/workflow/engine.go

@@ -158,7 +158,7 @@ func (e *Engine) advanceInternal(ctx context.Context, instanceID string, stageDa
 	}
 	currentStage := stages[currentOrdinal]
 
-	// ── Validation gate (v0.3.4) ──────────────
+	// ── Validation gate ──────────────
 	sc := ParseStageConfig(currentStage.StageConfig)
 	if sc.Validation != nil && sc.Validation.RequiredApprovals > 0 {
 		// Check for rejections first
@@ -296,7 +296,7 @@ func (e *Engine) Cancel(ctx context.Context, instanceID string, userID string) e
 	return nil
 }
 
-// ── Public Entry (v0.3.3) ───────────────────
+// ── Public Entry ───────────────────
 
 // StartPublic creates an instance for a public_link workflow without authentication.
 // The caller is identified as "public:<uuid>". Returns the instance including its entry_token.
@@ -358,7 +358,7 @@ func (e *Engine) AdvancePublic(ctx context.Context, entryToken string, stageData
 	return e.advanceInternal(ctx, inst.ID, stageData, inst.StartedBy, 0)
 }
 
-// ── Signoffs (v0.3.4) ─────────────────────────
+// ── Signoffs ─────────────────────────
 
 // SubmitSignoff records a user's approval or rejection at the current stage boundary.
 func (e *Engine) SubmitSignoff(ctx context.Context, instanceID, userID, decision, comment string) (*models.WorkflowSignoff, error) {